I usually just use the top of a stick of Chap-Stick to push down the weed or ash in the bowl. Lighters don't work nearly as well, so all my lighters are clean.
i'd be another finger user, i must be worried in the back of my head that plastic and heat don't go together well. plus my finger is shaped perfectly. actually i always have a safety pin handy to flip the bowl over halfway through...i don't like sucking green bud down into the bong water, and it tastes better when you flip it after years and years of smoking, we all develop funny little habits
yeah my lighters are black on the bottom cause I put my joints out on them I dont use them for my bowl.