cowl and A pillars rust, stopping and preventing it

[miller time]

hello i recently had my 69 charger worked on by macco, i had the cowl welded on and now i have rust inside it,  , i had already removed it and completely redid the cowl no rust and great paint, but they welded it on and the 2 brackets that connect it to the front clip. they didn't bother painting there welds so something that was simple, now is looking almost impossible. i don't know if they sealed the cowl on when they welded it or if its rusting between the cowl and car, i can see rust inside it from where they welded the front clip brackets (go from the cowl and bend vertical and weld to the front clip about 6inches long). how can i tell if they sealed the cowl on? I'm pretty sure they just welded it and now its rusting but I'm not sure because i cant see it. How can i seal it on and stop the rust? ospho and seam sealer? Ive also been spraying ospho in the a pillars with a spray bottle but it doesn't work so great, makes a mess and i don't think I'm getting full coverage, such as a way to but a straw on the sprayer?
i was also thinking of using one of those small flexible cameras to look around the cowl seams on the inside.

i went with macco because my first choice kept putting me off for 5 months, like i was going to trust my car to that guy, he kept getting "more important" customers, such as a corolla, dakota and other nonsense jobs, i told him the last time i saw him to get his schedule straight or to quit wasting my time

thanks for any advice

[Lennard]

Maaco is cheap for a reason.

[miller time]

am i the first guy to work on my cowl and a pillars? 
if you havent yall need to get on this stuff. the a pillars were never painted in the factory and cowl rust is a killer!

[billfury]

Try using this stuff from eastwood Internal Frame Coating w/Spray Nozzle Item #12515 Z.

It comes with a long nozzle that sprays out to cover everything.I used it in the unibody and other tight spots for my 72 charger and it works great.I cleaned what I was able to and then sprayed it.After it dried,I started cleaning all the under coating with a propane torch and diegrinder with a wire wheel and the little bit that leaked out from spraying was not easy to come off.Your going to have to take it apart to do it.Tape off areas you don't want hit with the spray and take your time. I hope this helps you a little.

[miller time]

thanks billfury, does that undercoat stop rust or only prevent it?

[billfury]

It's not a undercoat but more of a epoxy primer.It's designed for the inside of the frame rails so I would say it will stop and prevent rust.First time for me using it and I like it.Good luck.

[miller time]

thanks
i had my friend that restores mopar look at it and point me in the right direction, so hopefully i will begin work on it monday