I ain't never heard of or seen anyone going through extra "fire proofing" of tow,, when tow was used as wadding,, nor have I run into anyone that's serious about the accuracy needed for Trap Skeet, Target or today's sporting game/hunting that uses tow on a regular basis for wadding.
Today we have legal requirements,(game laws) and hunter ethics that didn't apply those many years ago. Game is more wary because of human encroachment, because of "seasons" and the mass of folks that enter their otherwise normal territory when season opens. We have to walk far into public lands, or own land or pay fees to hunt in any way near what was going on.
My point is, when I tried using natural and traditional forms of wadding for smooth bore I found the results dramatically different than when I tried a items for the smoothy that have a bit of a more modern manufacture.
I'm not saying a task can't be accomplished in a full traditional manner,, but then again as already said,, I haven't heard or seen of anyone fire-proofing tow.