Your guess is as good as mind as far as getting GIMP is concerned. I've never used it or downloaded it. I've just heard of it. I'm sure you can find it pretty easily without too much research. There are also free trials of Manga SAI out there, which is a great program, but I don't think the trials offers last for more than a month or so.

I'm glad I could lend a helping hand! If you don't already have photoshop, maybe look into getting the free GIMP version first. Also, a while back Adobe was allowing free downloads of CS2 - you can see if that's still going on. The size I make the majority of my images is 2550 pixels by 2550 pixels. Give or take. If that helps.

Yeah, my list keeps growing and I have a lot more on the way. I really enjoy doing them and it's great practice for my own work (I do comics). They often force me to learn how to draw things I never thought I'd draw. And those methods come in handy elsewhere. No, I don't use an app. I do everything in photoshop. First I get any needed reference material together for easy access. Then, in photoshop, I usually do a quick rough sketch of the image. Then I just start drawing the clean image step by step as seen in the tutorial. I draw in red for each step and then convert the line art to blue as I go along. And then I convert it to black and white at the end and then add color!