First time I tried I messed it up big time.
Best advice is to only spray very small coats each time. Literally just one layer for each coat and just use 4-5 coats or until it looks okay. Then make sure to spray it with a clear protective coating at the end.
Oh and sand it lightly before you spray, if it starts to get bumpy after any of the coats just give it another quick 1000/1200 grit sanding and wipe it down then continue spraying.
I sprayed too heavily the first time and it blistered on me, I thought it was the cold at first. Ruined my case, I had to spend months scraping and sanding it all down until I was left with just plain metal to start with again.