I have repainted or touched up dozens of bikes ( and my car hood).
Color matters a lot and black is without a doubt the easiest color to work with. I've touched up several black bikes. I typically use Rustolem enamel in the 1/2 pint cans and a brush and 800 grit wet with a block for touch ups.
I would start with the largest areas of damage to halt corosion. Trying to get it all perfect isn't going to happen. You can make it look pretty good.
I find it much easier to completely dismantle the bike and put it in a bike repair/work stand gripped by the seat post. That way you can turn and rotate the frame in all directions so you aren't fighting gravity. Areas to be painted can be level so you get less runs. This works much better than the wire cloths hanger on the laundry line method.
Wash all the dirt and grease off the frame.
Use green or blue painters tape to mask off the decals before sanding. Don't press it on hard and don't leave it on for more than a few days. Never use old fashion masking tape, that stuff is evil.
I use 800 grit wet to prep the area. I put water in a spray bottle and keep applying it. You want to get the area smooth. Rougher sandpaper will scratch up the surrounding paint. Edges of chips and scrapes can be feathered, they need it for light colors. Black enamel will fill in the smaller chips and scrapes.
Brush on single thick layer. Let it flow naturally. Don't keep brushing, just apply enough to cover and leave it alone.
Let it dry for a couple days to fully set up.
Then block sand with the 800 grit wet to smooth out the area. Go length wise with the frame tubes. going across will make low spots in the old chips and scrapes. If it gums up the sand paper, it's not dry enough yet. Sanding with just your fingers will get you lumps in the paint.
I use turtle wax paste to finish it up.
With those splatters on the frame, those can be replicated (before waxing) with a tiny brush or a q-tip and just dab it on.
Like i said, colors matter. Metals are very tough to match the density and size of the flake. Off colors are tough. silver and gold, aluminum and chrome paints are so runny. yellows are hard to match. The tractor color paints are usually very good. There are new texture paints but bikes weren't painted with those. They can be fun for creative paint jobs. I painted one bike with green sparkle that crinkled up for some Unknown reason. Looks like snake skin up close.
Rattle can spray paint can look good if you use 800 wet between layers. Last year I painted a frame in white. it took about 10 coats with 800 wet between coats. That is quite time consuming but it looked pretty good. the white didn't cover well so it took lots more coats than usual. I put water slide decals on and wanted really smooth paint so those would lay down well and stay stuck. I clear coated when done.
With clear coats, it's really easy to over do it. If you can see it, you put on way too much. Just light spray from a distance and stop. Let it dry and repeat a few times. There are many types of clear. Gloss, matt, crystal, lacquer, sparkle, etc.
I do most of my painting out doors but I have to move around to avoid wind blown dirt and strong winds.I always stand up wind so the spray doesn't blow back in my lungs. Spray painting indoors stinks up the house and requires a very good respirator. Brush painting needs lots of light, outdoors is the best. My garage is old. When the door goes up or down it shakes out a lot of dirt from the ceiling that lands on the bikes. I stained and varnished windows for my house in the garage. I put up big sheets of cardboard above the work table to catch any debris.
for some reason gnats are attracted to red paint so I have to put red items indoors to dry.
IMO a proper resto/repair means using the same kind of finish the bike had originally. Lacquers, enamels, epoxies, powder coat all look different.
Automotive 2-part paints are quite expensive. When I painted a junk yard hood for my car, the paints were over $200 plus all other needs. Same car got hit again in the fender. I found out I can order new body panels pre-painted and shipped for less than the paint cost. You supply the paint code (sticker on the car somewhere) and the age and they adjust for fading over time. I've seen plenty of bikes that were painted by auto body guys and they look like they were painted by auto body guys. Thick lumpy layers that hid all details on the frame. Lots of money for the wrong paint job. Auto paint suppliers can provide a rattle can size in any color code but those can easily run $80 per can.
I got a black bike a last summer from a neighbor who found it dumped in his yard. Turns out it was sprayed with Flex Seal. The entire bike! I was able to rub it off the painted areas with some finger grease. The original paint was in very good shape. Lots of the parts will need replacing because the rubber got into the components too deep to clean out. it was a nice fame so I'm rebuilding it for future use. I've seen countless bikes spray bombed black. A sure sign they were stolen and the thieves think black paint will disguise the facts. Anyhow, The Flex Seal actually looked interesting and could be good covering for a working urban bike. They are selling Flex Seal in other colors now including clear(?). Just note it will clog up cable stops, threading, etc.
IMO the most durable bike paints were some of the Chicago built Schwinns and the 2000s Treks. Again colors matter. Some were just tougher than others.
Removing paint from aluminum frame is best done with powerful chemicals, not any blasting or other mechanical means. MTBE versions of Kleen Strip works very well if you can find it to buy. It's pretty tough on flesh, you don't want it on you. Have large buckets of water handy in case. Bonded aluminum frames should never be dunked like furniture strippers do. There are some chemicals that dissolve aluminum (Drano).
In general the bike industry doesn't have color codes like the auto paints. Trying to match non-standard colors doesn't work well. Thats a major reason for a full repaint.
