Step 3 I double-clicked the image to unlock the Background layer and set its blending mode to Multiply. Then I created a new blank layer below it, to paint the matte into.
Step 4 Underneath these I made a third layer filled with a violently bright colour, to make it easy to see what I’m painting. At this point I stopped recording the Action. It will prove handy when preparing the other frames in the sequence.
Step 5 With a fairly hard brush, I filled in the dog with white on the matte layer. I wasn’t worried about rotating the image or making any adjustments; I just wanted to make a matte.