thats what i did when i had my 50,i bought the paid at walmart for 96cents and put a bunch of coats then a bunch of clear coats on it cost me like 10$ and i kept it for a little over a year after that and it held up mint,i did my swingarm to but i had to touch that up alot
i just hand painted mine the first time with oil paint, now i am getting it chrome plated, getting it free so y not,, the hand paint is solid, i coulnt even sandblast it off, its getting done in an acid kinda thingy
Spray paint is better on a 50 frame than a lot of people give it credit for. Its not like your boots/legs are rubbing on the tubes of the frame like a big bike. The only place it comes in contact with anything is where cables rub, and where roost hits the bottom most part of the frame.
Powdercoat is good, but in a situation where something is rubbing on it... it will not last much longer than paint. Powdercoat is near impossible to sandblast, but sands off relatively easy.
Ideally, powdercoat is the best choice. If you are just beating around the yard on the bike and not looking to impress any planet minis judges, then spray paint it and call it a day. Make sure you scuff up the stock paint to get rid of the shine. It should look flat like a primer before you spray it so the paint has something to stick to. After that give it a couple good coats and let it dry overnight before you touch it. Clear coat looks nice, and helps to protect the finish a little bit.