Select a paper from a kit you want...
and a mask you like to go with the tube you've chosen
take the paper into your psp, DUPLICATE it Shift+D,
close the paper now go up to layers, and click "new mask layer"..
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right click on your layers pallet and Merge Group.
make sure to uncheck *invert mask data* Click ok, you should see this.... Hosted on Fotki
And this is what you get: