I have spray painted couple of frames with Rustoleum. With proper technique and patience, good results can be achieved, but durability is not going to be very good. Numerous thin coats is better than a couple of thicker coats. The first couple should look like the frame is NOT getting good coverage, consistently lacking. Also, I have had a couple of frame sets power coated, which would definitely be my choice over DIY if I was doing another frames set. For the cost, time and effort, considering the final appearance and durability of the finish, powder coating is, IMO, superior.
However, I kind of enjoyed the whole process of DIY painting, and I liked the result, knowing ahead that the durability would be low. If it is something you want to give a try, do it with realistic, or no, expectations.