Did he blow-tube? Many BPCR shooters today still blow-tube and will shoot the match without any loss of accuracy over as many as 80+ shots.

I corresponded with the Mad Monk, aka Bill Knight, nearly 20 years ago.  He did chemical analysis on many powders including samples of  original  batches. He said those 19th century powders shot much cleaner and shot to shot fouling was not an issue like it is today.  If my memory is correct,  , buckthorne alder charcoal is critical to producing top quality BP.

I just remembered Pope advising "blowing the barrel"  if the next shot was not loaded immediately.  I believe that was in reference to ML the next bullet.

Edit: I think that was in the Pope's Barrels book.  Can't recall the exact title.

U R welcome     

One of the problems is "common knowledge" was not mentioned or recorded. Either everyone knew what to do or it wasn't an issue, eh?

Good luck with your old powder,  It will be interesting to see if it shoots clean.

Schuetzenmeister
If blow tubing was "common knowledge" (it may well have been) it seems odd that no one in the Schuetzen game wrote of it, at least not that I've come across. Details about seating bullets to the top cannelure in his cases and that he did not clean during that day's shooting were stated but no mention of blowing.

Boats
Thanks for jumping in. You raise a good point about humidity. That's one that would be difficult for me to test. Here in the Az desert, unless a storm front is moving through, average humidity is below 40%

I wouldn't be too sure about it being mentioned if being common practice.  When reading contemporary literature regarding long-range shooting in the UK, especially about the period when cleaning between shots wasn't permitted, you will have to search a lot to find references re. blowtubing or breathing down the barrel, it simply isn't mentioned by most, as it was considered to be common knowledge.  Only Halford gives it a brief mention in  'The art of shooting the rifle', but other books (Including Stonehenge, which is considered to be a reference work) don't mention it at all.  Kinda like why state the obvious?  But you do see some blowtube contraptions surfacing now and then at auctions - few and far in between, admittedly, but they are there.
And while some contemporary BP's might have been a bit cleaner burning than what we have now, don't forget it still remains black, the composition hasn't changed - meaning it will leave quite a lot of solids behind after firing.

MarinBelgian
Please don’t take this as non-acceptance about it possibly being common knowledge that the old long range shooters used blow tubes. My understanding is the jury is still out on that being settled, factually. I’ve not done research on old time long range shooting but it seems the historical reference is only Halford’s The Art of Shooting the Rifle. Please set me straight on that, if I’m wrong. 
I think a decent argument could be made that "those blowtube contraptions surfacing now and then at auctions", were in fact used by shooters to blow a small mouthful of water through the barrel. Followed by a dry patch on a cleaning rod to push out the fouling, then another dry patch to remove residual moisture. In addition, the water would have a small cooling effect on the barrel. After all; if it were “common knowledge” nobody would have written about it, right?
My point is not to cast doubt on whether the old shooters used blow tubes or not but to confirm they did, additional old references need to be found.
In the Schuetzen game, which is my reference here, is that I have found no references to blow tube use and that story I referenced, stated that Strecker shot all day without cleaning. Based on that story being factual, I’m asking if any one knows how that might have been accomplished. Using a blow tube is one possibility.