On the iPad, I use Zen Brush to practice my brush strokes. I highly recommend it - works well and one button erases the character so you can quickly do a lot of reps.

However, does anyone know a good Mac based program to do the same with a Wacom? I'm not looking for character entry, recognition, etc - just like a slimmed down version of Photoshop that would let me draw characters, and easily erase them. Seems incredibly simple, but not sure how I would do it. (Photoshop is way too clunky for this).

Try this one that I like very much :
http://www.artrage.com/artrage-demos.html
Or this one:
http://opencanvas.en.softonic.com/

(sorry, the two aren't free. Art rage has a free edition, though)

Personally I do most of my writing practice with my finger/palm or on good ol' ink/paper. I tried doing things digitally when I first started but it really doesn't have the same feel.

http://incompetech.com/graphpaper/genkoyoushi/ (If you ever want to make your own Japanese grid paper)

OneNote (part of Office) can be used as a writing pad with a tablet. But I haven't tried out the Mac version of it. Though I might be able to try it soon.

If you were on Windows, I'd suggest Windows Journal.
http://www.fluther.com/23571/is-there-a-...l-for-mac/
So maybe you should check out the programs listed in the link above.