I always run my brass pick into the touch hole before priming. I was taught that it makes a flash channel into the center of the charge, promoting better and faster ignition. Since I pick, I don't feel the need to blow down the bore to clear the touch hole.
When I have seen folks blow down the bore, I've seen some sort of half-heartedly blow "at" the muzzle. With no "seal", I am pretty sure they aren't getting enough air pressure in there to blow anything out of a 1/16" touch hole. Do the rest actually stick their lips to the muzzle and really put pressure down the bore? Serious question.
Different strokes for different folks. God Bless, and best wishes, Marc