It's all in photoshop and done with a tablet (intuos). I gave painter a go and it's awesome except i couldn't fix some horrendous colour reproduction (banding) nomatter what i tried, and this seems to be a common problem with it. Doesn't really matter what software you use, so long as you know shortcuts to make your life easier. I'm well accustomed to photoshop so i just use that for everything.
Mainly for photoshop:
Hold down space = pan tool
R = non destructive rotate canvas
F6 = Colour palette
For the occasional perspective guideline or adjustment layer i'll use the mouse, but everything else is done with the tablet. A good thing you may want to do is to make sure you map your tablet in a 1:1 ratio when using Pen (as opposed to Mouse) mode. I have my pen customized so it's easy to toggle between both modes.
I've barely done any painting/drawing in real life, but the same principals apply. If you want to do some quick sketchboard mockups it's easy with a lot of custom brushes (shapes, etc), but it's not rewarding and the end result feels tacky, so i always try and draw everything as if in real life.
This is only a hobby for me i havn't put any serious time into learning any anatomy/proper landscape, so I draw from reference quite often.
If you do have the time and money, the one place i'd recommend checking out is
And really the best advice is practise do redo repeat do more experiment rinse repeat.