On my 16.5" I use a metal spatula to do the same thing. About 3 cooks then push the ashes to the back. Another 2 or 3 cooks then clean them out.
Sometimes I'll take the lump basket out and just sweep the ashes to the sides. Accomplishes the same thing, extending the time before full ash clean out.
I'll have to come up with something for the 19" because I'm sure the spatula won't be long enough.