Still Biting

I know you have many questions on biting, but I have looked and none of them seem to answer my question. Our Jack Russell, Roscoe is a very good boy and we have had him in Puppy class as well as in home 1 on 1 training. He is ready for agility classes, except that he is 10 months and we still cannot seem to get him to stop mouthing. He doesn't really get agressive and his biting has curbed a lot, he just likes to put his mouth on us when he is playing. My concern is that he is not really a puppy anymore and that seems to be puppy behavior. We still use the squirt bottle and the firm no bite. We don't really like to grab his muzzle as it makes him more agressive. I am just wondering if we are missing something? He is very well trained, it's just that area that we can't seem to control. Any suggestions?