AJ, just wanted to first say thanks for all your great info; I found some posts of yours in a Viper forum, watched a lot of the videos, just ordered your namesake Adams bundle and hope to get down to some detailing soon. I have a black chevy pickup that's not in the greatest shape that I plan to use for learning before I touch the 'nice' cars.
Anyway, I've always used the two bucket wash technique with grit guards, but the truck probably gets washed twice a year at most. As a result, it has a lot of nasty crud built up on the lower front quarters of each front door. Even after washing, little bits of whatever are still there. I haven't done the foam pre-wash before, I ordered the gun and will do what you do in your video for that before the next wash, but I'm wondering where the line is before how much pressure you can use while washing to get some material off versus moving on to clay bar with the risk of it marring the paint? In your video with the clay it looks like you use a fair amount of pressure; I'm afraid with the kind of gunk on my paint that could easily put deep scratches in there; I feel like I have to get that stuff off somehow first, but maybe I'm just naive from having never used clay before?