thank you, one and all, for the responses ... i am not now smarter, but a good bit less dumb.
emboldened, i tried some aquafortis (Track of the Wolf that's been in my basement a long time). Regrettably, when i went to blush it with my handy dandy (el-cheap-o) heat gun, it went from the weird green to scorched in about a half second. I tried a different spot at a lower setting ... same result ... then i went to the barrel channel and tried a hair drier, and it wouldn't blush at all.
In my frustration, i forgot that you're not supposed to do that, and now there's a light spot of rust on the underside of the barrel ... wisdom is gained from experience, and experience is gained from bad decisions ... so how come i'm not the smartest guy in the world?
So, the 'dumb question:' can aquafortis go stale? Is what i'm using past it's 'sell by' date? Or am I doing something to cause this problem ... unfortunately, i don't have any scrap ash, and i'm pretty much out of spots where whatever i do won't show.
I'm about to give up on this aquafortis project altogether and just use some stain. (and swearing ... lots and lots of swearing ...