Yes I am dong the DSM method kind of funny because I too started in the car world as you can see by my and your user name and when I first saw DSM you can imagine what I thought they were talking about ha ha.This is also my first time trying dry start "crosses fingers"
As far as using plasti dip I have used that stuff before and was never really satisfied. Not saying it wouldn't work because I dint try it for this. Also there is a large difference between being waterproof and being submersible. Damn universal solvent.
Yeah I've never used it submerged for a long period of time either. So I'm not sure how long it would hold up either but the theory of what it should do make it sound like a decent candidate for this but who knows. I saw a video of it holding water in a cardboard box without leaking at all so it would be interesting to see what it could do long term.
Tank looks awesome though. Makes me want to start another small tank. Haha