Wow, this tutorial is a life saver! It's probably the most helpful GIMP tutorial I've seen. I'll be using these tips for my future deviations. There's gonna be a part 2 on shading, right?

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I've got nothing inspiring to say.
Yeah.

Oh course. I'm working on it today, should be done by tomorrow or the next day!
And yes for best compliment ever! I've always found GIMP tutorials lacking, and its still my program of choice.
Go Gimpers!

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Why is it every time I need to get somewhere, I get waylaid by jackassery?

I find GIMP to be almost as good as Photoshop without the huge price tag.
May I ask how did the lineart? I work fine with pencil and paper but I've got no scanner or tablet. Pretty much anything that I upload will be done digitaly.
Then again, I've seen amazing works from MS Paint.
[link] <---This person did the Mona Lisa. My jaws dropped the first time I saw this.
[link] <-- This one's also awesome though it has nothing on the Mona Lisa

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I've got nothing inspiring to say.
Yeah.

Well, since I have a tablet, I use the ink tool and basically trace shitty sketches. I'll show how to do that in another tutorial, since I'm on a roll right now.
If you're using a mouse (though I've never managed to do this, my digital career began with a tablet, I suggest using a small paintbrush (like 3 or 5, depending on the size of the scan) on a layer above your original sketch. I would leave the sketch at the original scan size, too, just because when you zoom out to your preferred size, mistakes are a lot less noticeable. Make sure before you do the whole thing, you zoom out to the size you want it, to make sure it's not to thin or thick. I use this technique sometimes to save myself some grief with ink.
If you're just using pencil and paper, and scanning, I'd suggest using an inking marker or ink to do the line art, then going to Colors --> Color to Alpha and choosing white (or w/e colour your background is). (You'd have to clean it up a bit, usually). That makes the lineart into a transparent layer so it's easy to shove a layer underneath as a background.

Sorry for being so wordy. D: Hope any of these help.

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Why is it every time I need to get somewhere, I get waylaid by jackassery?

Are we gonna get to see the finished piece?
BTW, I found this helpful even though IDK if I WILL actually help in PS >___>' xD
Just to see how someone does it~

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^{I count the} dead bodys like sheep _{so I can finally go to} sleep
[link] mmm braaains...I mean peniiis
*PendeoClub ^{per se'}
Fiancee':~Douchi
[link]

I'm sure it will, most of it is pretty transferable...the biggest difference between the Gimp and PS seems to be terminology. (Most of the tutorials I follow are for PS)
Yes, you will. Right after I complete Part 02: Shading.

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Why is it every time I need to get somewhere, I get waylaid by jackassery?

oh-ho~ |D I shall be waiting <3

And question about the trade O8 -I got the BG finished and almost done with the lineart- Does uhm... he have a snail trail/ happy trail? You know, pubs goin down from his bellybutton? (Or course you knew. ._. )

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^{I count the} dead bodys like sheep _{so I can finally go to} sleep
[link] mmm braaains...I mean peniiis
*PendeoClub ^{per se'}
Fiancee':~Douchi
[link]

ahahaha...If you'd like, but thats up to you...sorry for the late reply. (Personally I like em' fairly hairless lol, but it could work too. )

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Why is it every time I need to get somewhere, I get waylaid by jackassery?

I'll just put a little then~ <3 Jimmeh has them...
(personally I love snail trails |D they make meh happeh~)
Would he really... take the time to shave himself nice and clean down thar?

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^{I count the} dead bodys like sheep _{so I can finally go to} sleep
[link] mmm braaains...I mean peniiis
*PendeoClub ^{per se'}
Fiancee':~Douchi
[link]