How should I clean my AR15?

I have a bushmaster M4 type carbine. Everytime I go to the range I shoot about 80-100 rounds. I do a very extensive cleaning whenever im done shooting. I always clean the upper by removing the bolt carrier then I take some hoppes and a toothbrush (not my own) and go to town getting every single nook and cranny. Then I dry it off and take some paste like lubricant. I put a dab on my fingers and spread it about lightly so everything is smooth. However, how do I clean my gas tube and the area around it? And how do I clean the lower? Thanks!