I've used a candle - a lot back when. Works fine but it's a bit tedious, so there's that jar of inletting black. I have no idea what brand it it as the label disappeared long ago. Apply it thinnly and it lasts forever. when it gets thick and pasty, add a drop or two of paint thinner. You don't have to thin the whole jar and get it smeared everywhere, just the stuff on the top.