Chicken on a Brinkmann Smoker N Grill I've been trying to smoke chicken for many days now, but the problem is that most of the time the chicken tastes like a match. 

I've done everything, soaked the wood for a long time, cooked it with indirect heat with a pan of water in the middle. I have tried both wood chips and big pieces (soaked and dry) and, of course, all that with charcoal. Can anyone please advise me?
Sounds like you've may have two issues. Too much wood and incorrect expectations.

First it sounds like you've "oversmoked" your chicken. Depending on what kind of wood you use too won't need much for chicken (remember it's a lightly flavored meat.) try less wood next time.

Second that "ideal"temperature is great off you want pulled chicken but it will not do god things to the skin. Try either smoking at a higher temp for a shorter time, discarding the skin or finishing it on a grill.

Lastly if your meat had a bitter flavor it could be that you had live flames rather than embers as you smoked. Remember that you want to avoid flareups as much as possible.