MMMm sounds like possibly too much paint. Although, I am not sure if MM Primer is the same as the Testors primer or not.
Thats what I use is the Testor's Primer in the spray can....would like to try the Tamiya stuff, but can't swallow the $14 a can that most places want....come on, is it really that good?????
Sorry, back to the topic at hand.....I used to spray it right out of the can, but always thought it went on way too thick...so I started decanting it from the spray can to an airbrush bottle, and then adding a few drops of thinner to it, seems to work a little better. And one coat of primer has always done the trick for me.
Now having said that, the MM Primer maybe different again I don't know. If its part of their acrylic based line, I have found them to be very thin to start with.
If you aren't too far along on the kit, and you want to strip the paint off and start over, get your self a bottle of Castrol Super Clean from Walmart, soak the kit in it and the paint will practically fall off the kit.