Depends on how nasty it is, 5:1 is a general purpose rule. (5 water:1 WHITE Vinegar) I just dump it in until I think it's good enough. I run the pump overnight sometimes in the solution. Any soft brush will work, bottle brush (as you mentioned) toothbrush (wife's works better if you have one, girlfriend's will work good too) I use a soft bristled basting brush.