As I have just dabbled a little bit with alphas (doesn't make me any good at it yet) I can share what I've learned so far.
The basics is alphas are greyscale maps. 100% black is transparent, 100% white is opaque and you can get semi transparency with greys.
1) Learn from the pro's :p
Michael McKinley has done two tutorials on Alpha masks. One with how to set up image planes in the free video tutorials section or through his website (www.mtmckinley.net
) I forgot which. I highly recommend this one as it explains technique. How maya works etc
The other video was through simplyphotoshop when that existed. This video is also good because it shows what alphas can do. Concepts.
Found it: http://www.simplymaya.com/movie_page...html?tut_id=93
2) Learn UV unwrapping. You will have total control where things go. Very controlled painting.
3) Images are complex yeah. I found it helpful to look at ref and convert ref images to black and white to remove some of the complexity. Colour is just distracting information. A black and white shows the outline and characteristics better. Find any feather image and B&W it and study before you paint your alpha mask.
4) Patience. They are finicky and tricky. Persistance is what will get the job done. I should have spent more time with the alpha maps. Feathers I believe can be tricky to paint. Both hard edges and the wispy qualities and overlaps.