For processing photos of the Milky Way Photoshop is fine, in fact it really doesn't get much better for wide field stuff.
You probably want to try stacking multiple exposures to help bring out signal and reduce noise. For this you should check out DeepSkyStacker (it's free).
Once you've stacked some images in DSS then you can process them in Photoshop.
http://deepskystacker.free.fr/english/index.html