Glenn,
With wood stoves, the secret lays with well seasoned wood, next years wood is cut this winter, stored in a covered shed and keeping hot fires. I have heated this place for thirty years, never a chimney fire or creocote problem. I have never dropped a chain or brushed the chimney, with a mirror and flashlite can see the length of the chimney, nothing sticking to sides it all falls down into clean out. I keep my stove pipes clean, taken down monthly and brushed out, they are dry no buildup. The flue must be warm. cold air sinks warm rises, the column of heat has to be stronger than cold air to get good draft and the chimmney must be the right size to big and it don't work to good. It would seem to me that a forge fire is different than a stove fire so you venting must be larger as in a fireplace. On a safety note a box of baking soda will snuff a chimney fire quick is handy to have in the shop I also have fire extinishers but can reach that box of baking soda quicker. I want to build a add on to garage just for welding and a forge, I saw lumber for a living so their is plenty of fuel, to weld now I have to major clean up, real pain.
Adirondacker