Spray bombs??

The motor will be pulled very soon and the engine compartment stripped. I will not be repainting whole car (this time a round). The engine compartment "was" the colour of the car, however I ending up painting the inner fenders gloss black as the compartment was quite worn with scratches ect. I would like to try and get it back to blue before I put the new motor in.
I can get a very close color match "spray bomb". Although I know this is not within the MOPAR law...and a bad way to go, I have read a lot of negitives about using any spray bombs but...I'm still wondering if done correctly......has anyone had any good results where their painting turned out not too bad or better then exspected.

If so any tips for me.

PS..Going to a shop is out of the question until the whole car gets re-painted and I'm not set-up or have the equipment to do it pro.