AIO doesn't layer, from what I understand, so I think the point of two coats is that the first coat cleans and preps, and the second coats, um, cleans and preps even more. Just to be sure. It made sense to me, so I did it. Besides, you use so little that it's cost-effective.
I use two small MF terry applicators for AIO. I followed the 2x AIO and on the second application the MF did (slightly) discolor so I must have missed some spots on the first AIO.
Thanks - I decided to apply AIO by hand. It seems like I'm using way to much product, but if I don't than it starts to streak when I'm applying it (like I'm wipe it off on the back stroke). I got a little better with it and will be sticking with one coat. I applied a second coat to the hood and it did'nt seem to do much.
I followed YoSteve's application process with AIO on Son's '91 S10 Blazer (white). Applied first coat (by hand - MF applicator) to entire vehicle and then followed with a second application (again by hand) without removing the first application and finally removed by MF towel(s). We preceeded this process with a wash and spot claying. The AIO went on and came off easily.
As a result of the claying and AIO application, the surface was left with a very smooth feel, but there was very little gloss or shine. The vehicle was only very mildly oxidized. We are going to try applying the AIO once more with the PC and a polishing pad.