Tutorial 1:How to choose and mask an Image Hose

First, choose your primary Image Hose.  This
is done by clicking the topmost, large image
in the brush attributes floating window:



If this window is not visible, select the
Window Menu bar, and select "Show Brush
Settings".

Next, to have a normal combination of the
Image Hose you choose with the primary Image
Hose, select the Image Hoses menu, and
Subtract Image Hoses.



Select the Image Hose mixer icon in the
Brush Settings window, and choose the black
and white circle.  



That's it! Now you have a round Image Hose
to paint with.