I have no idea concerning the plastic taste; I never went through that. The tamping is easy though: you tamp whenever necessary. If the draw starts getting 'airy', it needs a tamp; otherwise LEAVE IT ALONE! Just let the weight of the tamper compress the ash. You don't want to compress the unburnt tobacco; you already took care of that when you loaded the pipe. If the airway is getting plugged, you ARE using pressure-stop it!