I'm spray painting over the original paint on a very old steel frame, mainly because I can't find the color I want except in spray paint and I don't want to pay a pro yet to take a chance on a color I'm not positive about.

Are there any suggestions for which spray paint to use? Should I add a clear coat of some kind for protection?

Most bike paint is enamel. So an enamel based primer/paint/clear most likely work. Very few lacquers were used in production. Spraying a lacquer over an enamel can be problematic so if in doubt test on a "hidden" spot. Andy

Thanks! For some reason I thought frames were usually powder coated. In any case, enamel sounds great. Thanks again.

You qualified the age of the bike to what I think would be before widespread use of PC. Andy

I think the frame is between 1978 and 1984.

If it were powder coated, would that change the choice of enamel?

Powder coating comes in any color you can imagine. Depending on what kind and level of fancy you want it runs from $100 to $500. It's the prep work & set up you are paying for. Any reputable PC'er will chemical strip/media blast, de-rust in a phosphoric acid bath, passivate, then process in whatever color you want & be done in about 1 to 2 weeks.

You end up with an essentially new frame in any color you can dream. I favor Prismatic Powders high gloss, but it comes in a variety of gloss levels, textures, candy, chrome, transluscents, etc... Painters claim paint is better coverage & rust protection. PC'ers make the same claim. Both are more durable than spray paint from the home improvement store.

1 gallon of stripper, 15 dollars
3 cans of primer, 24 dollars
3 cans of Rustoleum Enamel 24 dollars
3 cans of clear gloss 24 dollars
sand paper, time, etc...no phosphoric acid derust/passivation dip

My money says a single color, 1 shot powder coat will be cheaper, simpler, and more durable finish than a home job.

If it takes 3 cans of each paint, primer and clear coat to do a bike frame you have an EXTREMELY large frame. One can can do multiple coats.
If you've done painting and familar with and understand the full prep (98% of the work), you can get a decent quality job with rattle cans. No match for a proper powder coat but can still be good. You can pick up a can, wipe of dirt and paint it to. It is up to your expectations.

A frame takes more than 1 can & multiple coats means 2 cans is pretty easy to get in to if you are patient and consistant. The 3rd is because you will run out mid job & the hardware store won't have anymore in stock. So, still, subtract a can each for the return receipt & you're still into the job $75 plus miscellaneous.

The whole "drop-off, pick up" aspect of powder makes labor considerations a no brainer. It would just cost too, too many more dollars in my time value alone to do a rattle-can job at home. Let alone the quality of the final product done by professionals would be head & shoulders above. Worth considering.

Sounds like you are going to do a temporary paint job until you figure out what color you want from a pro?
If that is the case go to the local Do it Center Home Depot Lowes whatever and get the cheapest paint you can find, $4-5 a can. Buy 2 of each primer, paint and a clear about $30 plus some 600 or so grit wet/dry sand paper. Sand the original paint wipe it down with lacquer thinner and primer it sand the primer with wet sandpaper put on a couple of coats of primer sanding in between then spray the color do the same sand wet then the final clear no sanding. It won't be the most durable finish but assuming it is only a temp finish it will be good enough.

Satisfaction of doing a job yourself --- Priceless

And to add yes I have done exactly this, I wanted to see if I wanted a mat/satin finish as opposed to a glossy finish or not.

Exactly right. Thanks for the steps.

I'll add one step in here.. Use a purpose made tack cloth ($2) just before any painting, not between coats but any time after sanding or away from it for a few hours. Chemically cleaned and lint free are musts and honestly each of those steps only takes a few minutes.. If sanding between coats I switch to super fine steel wool instead of sandpaper myself, I find I can do a more even and controlled sanding of pipes and round things like frames vs sandpaper..

Good idea; I understand what you mean. One of the reasons I inquired about a clear coat is because in testing different colors on different sections of a scrap tube I noticed that I could pretty easily scrape away the paint with my thumbnail.

Rattle can paint takes a long time to "dry". It may be touchable in an hour but will still be soft for a while (like days/weeks). Stuff like rubbing alcohol can soften and wipe off fresh paint even days later. Thin coats and following the recoat times which are on the can and usually a few minutes to 1 hour and then not again for 24-48 hours. That will make sure all layers can dry good, example.. Example.. you don't want to put clear over paint too early, the underlying paint will never fully cure correctly. Mr personally.. I use matt/flat paint if I am putting a gloss coat on top. Using a gloss paint requires more work to scuff up before putting a gloss coat anyway. Either use gloss paint and be done with it or flat and put a gloss coat on top.