If your cleaning solved the bitterness, congratulations and smoke on.
I've always followed CS's instruction to wipe down excessive interior grease in my AQ with a damp rag after every cook. !0 minutes well spent and very little build-up ever. I also clean everything that touches food after every smoke. Just basic sanitary practice. Otherwise people who see the inside of my smoker won't want to eat whatever comes out of it.
What I do when I feel it needs a cleaning I line my wood box with foil, put about an inch of water in it, turn it on, wait for steam to come out the vent hole and shut off and unplug it, wait 10 to 15 minutes, and wipe down the inside.
Wear gloves and use caution, it's hot.
sounds pretty risky to me but if it works,..............