I've never used Vallejo paints so I'm not sure what went wrong, but don't give up on the masking yet, you may be able to save it. Can you post some pictures?
Where we last left off with this one I was having canopy/landing gear issues...I want to get this one done to start a new project so we're gonna go with the diorama route I believe. Belly landed Do-17, my only issue is the codes on the side could potentially be wrong, also need to find a base big enough