Hrmmm... The best way to take all the gunk off cast iron is the cleaning cycle of the oven and a metal scouring pad. With wooden handles, it becomes a lot more difficult. Yoiu're essentially left with getting it red- hot (literally, red-hot) on a grill or (last ditch choice) your kitchen stove and then letting it cool and getting after it with a wire brush and scouring pad.
Once you've got the gunk off, you'll need to reseason it. Take your lard/ tallow/ ghee/ whatever and apply it liberally to a warm (not so hot you roast yourself pan, all over. Put it in the oven (upside down with a cookie sheet on the lower rack) at 450- 500*F for several hours. Pull it out, use it for only greasy things for the first several months, and be nice to it.
(There are other MUCH more precise websites on how to season your cast iron out there.)