I don't blow down the barrel. I think I'd need to understand the science and how a very minimal volume of air, blown thru a barrel at extremely low pressure, with high relative humidity but minimal volumetric moisture can actually soften fowling before the remaining heated air inside evaporates the moisture to the point where it has zero effect on the fowling created from extreme heat and pressure.
I guess if you are committed to this, you carry around and use one of those blow tubes to keep your mouth off the barrel and residue that is likely known to be a carcinogen to the smart people in CA, to maximize the air volume and pressure through the barrel. However, with the right lip-to-barrel or nipple contact, I do wonder if it is possible to blow Reveille.