I did my Yugo M70 AB2 with a $6 can of Dupli-color 500 engine enamel. Applied correctly, cured correctly and then baked, it has proven an excellent, durable finish.
On the other hand, I sent my Kel-tec PF-9 slide to CCR Refinishing for a Cera-hide ceramic finish over 4 years ago and it has held up flawlessly.