I see nothing wrong with a rattle can paint job. I have done many rattle paint jobs. To get them to turn out nice its all about the prep work. Sand all the clearcoat off if you dont strip the whole frame bare. Use the best primer you can afford and do 4 or 5 light coats spaced about 15 to 20 minutes apart. The real thing to a decent rattle can paint job is light coats. Also use some type of clear coat. If you can afford it, this product here is the best clear coat you can get.
Spray Max 2k High Gloss Clearcoat aerosol
Its a 2 part gas proof clearcoat. I used it on my KZ400 tank and it worked out perfect.