On reading this discussion, I wonder whether some alternative approach might
be better for small-volume home etching. In particular, instead of moving
the etchant around the board, perhaps move the etchant *with* the board.
For example, attach the board to a shaft of some kind, dip it into a tank of
etchant, and spin the shaft and board?
This would seem to avoid at least some of the problems of spraying the
etchant.
Mike C