making blur work

[RobertFrick]

The biggest effect I found today was size of image. In the picture below, both blurs are made with a pass back and forth at the same settings. For the top, the size was 1500 x 1000. For the bottom it was 600 x 400. That's a big difference in effect. (The picture for which I could not see the blur was 1298 x 1728.)

Rate also seems to have an effect, as does opacity. But not enough.

I am guessing that GIMP is slow with a large brush size and a small brush size doesn't capture enough area to be effective.

Thanks again.