TL;DR - Good quality 2k clear coat. Either pressure pack or through a proper gun. I use cans with the primer in the bottom.
Long version:
I've been using 2k clear coat over almost everything I have ever had my hands on.
I'm not big on 'restoring' bikes. I think of each of the scratches, dents and "patina" as a bit of a story the bike has to tell. Whether its been old BMX's, 60/70s dragsters, road and mountain bikes... good and shit ones. There is no doubt a crash or entanglement that every bike I've ever owned can tell me about. I'm a bit the same with steel tank/frame motorbikes.
So I 2k 'em. I pull every part off the bike. I do replace things that are rooted or servicable. Then give the f&f a super light (2000grit) rub down, then a quality grease and wax remover. The waxngrease remover is key cos you'll fk the bike if its got even a smidge of grease or wd40 or some shit like that on it. Then I clear coat.
They come up looking sick. It seals in the awesomeness. In your case, if the bike is in great nick already, it will preserve that.
If I have sticker corners lifting, I poke the corner down with a toothpick after the 1st clear coat. It resticks with the tack of the clear.
Once cured, I put them all back together then I ride them to my corner shop and bakery and park and through the city until someone inevitably says "hey thats cool." Or "I had one of those" and the bike in question ends up in their possession. Then it starts again...
2k clear works great. I do want to point out to you though that I've not owned any bikes of significant value. No one offs, no team bikes, nothing with pedigree. All low to mid range, but brand named riders. But bikes that were once the best in the fleet in their owners shed.
I've had a '72 Malvern Star 20" long frame cruiser for about 25 years thats had this treatment and its still as good as the day I did it.
