My solution to ash build up is to block the ash with an open end can. I found a can that was 2" tall and 3 1/4" across. Cut out both ends and place it in the bottom of the Weber. It fits under the charcoal grate. As ash falls thru most builds up on the outside of the can leaving the air vents open. I think the can was a Frito bean dip can.
1980 Bigfoot 17' & former owner of 1973 Compact Jr