Chicken is easy.
My only guess is that if you're still seeking the perfect brisket.. where did you get that first brisket from? The quality of the meat is a big thing.
I know my briskets from the butcher always come out nicer than any I get from Wal-Mart.
Not to say the ones from Wal-Mart aren't good, but my "perfect ones" come from Kavasovic's, that chit is GOOD.
Other than that, have you tried changing the smoke a bit? What wood are you using? Using too much wood? Did you use briquettes or lump that first cook?
Loooots of variables.
Usually the best way to do it is to start off as simple as possible, and get more advanced as time goes by.
Dalmation Butt rub, some oak or pecan or hickory or whatever you prefer... go from there.
The Life of the Knife is Ended By! The Wife.