Looking at answering your question, but need info. Is this a UDS, or double-barrel smoker? I think you mentioned UDS, but in the initial post you mentioned two barrels. I build double barrel smokers, and on MINE, I do have an ash hole (love how that sounds...LOL) I simply put a square hole in bottom of the bottom barrel, with a slide to close it off. Easy to rake ash to that hole when cleaning out.
"I'm not completely worthless...I can always serve as a bad example!"