J.G.
If he is putting his pee in the potty, he is more than ready. The most important thing to do is to be patient and gentle. Do not expect him to just "Be trained." It's like learning how to walk. they fall down a lot, for a long time. Some kids never wet their pants after they train, others spray them a little, etc. Each kid is different, but the process isn't linear. LIke learning how to walk, there are ups and downs.
Just keep telling him that when he feels pressure, you go to the potty. When he has an accident just say "that's OK, next time we will keep our pants dry." Just keep at it, and he will get it.