Leather from Craft Foam
This is a variant of my finishing method - explained here - that I found by accident. I was being rushed for a project (aren't they all like that when you get close to the convention : P) and I was cutting corners on my paintjob and it gave interesting results. I got a very "organic" finish that reminded me of leather (you know how leather is not exactly the same color all over)
For all the detail on my finishing method, please follow the link above - I will only explain the differences here.
So the trick lies in Step 1 and 2 of my finishing method - let me explain:
Step 1 - Flexbond
In my original finishing method tutorial, I'm saying that the purpose of this step is to seal and smooth out the foam. Well since you're trying to keep an organic feel for leather, smoothing the foam becomes less important. Having a bit of the pores from the foam showing through the paint job will make it more believable. Also, the trick here is to create a "layered" finish. Flexond has a certain thickness to it - so if you don't spread it thoroughly when applying it, you'll create an effect of layers (some spots will be raised and some lower than the average thickness of your piece after the Flexbond).
Since this is exactly what we are trying to achieve - you should be making sure you're NOT doing a good job at smoothing out the foam. This means applying a lot of Flexbond and not working so hard at spreading it.
Step 2 - Paint
The trick here is that you have to wait until the Flexbond is almost cured - but not totally cured. The line between "almost" and "totally" here is very fine. It's kind of hard to explain on how the piece should look at this point (before painting). What I can tell you is that I usually wait a little bit more than an hour from the time I cleaned my brushes from the Flexbond coat (so I finished the whole coat on the whole piece I'm working on). Since I applied the Flexbond "crudely", some spots (the lower layers) will be completely dried by now... but some of the thicker spots will not be quite dry.
Then it's all about applying the paint crudely as well. Usually I would make sure I don't spend too much time over one spot, kept a good movement over the piece while spraying paint (to keep it as even as possible) - but here I just don't spend so much attention on this. We're trying to keep all this organic, uneven (just don't try to hard - you'll end up with something that look like a crappy paint job, not an organic paintjob : P).
When doing leather - I also try to use craft foam that will be darker than the color I'm trying to achieve. I'll be using the color of the craft foam to "shadow" the color of the leather piece by only appling a thin thin coat of paint in some place so that the craft foam color can "shine through".
Step 3 - Flexbond
Same thing as the finishing method - nothing special here
Step 4 - Varnish
Here I usually put 2 coats of varnish - 1 matte and 1 gloss (in that order).
Leather is not matte - it "shines" a little bit. So the first coat of varnish (matte) will be to make sure I get rid of the stickiness of the flexbond. After that I unevenly apply a thin coat of gloss varnish. This will give the little shiniess required for a believable leather piece.
The great thing with craft foam is that it's flexible. Once you've used my finishing method, the paintjob doesn't care about the flexibility of craft foam... the paint will be as flexible as the craft foam (it won't chip). The great thing for leather piece here is that you can make it look use by "chrushing" the craft foam (in your hands) when everything is cured and dry. This will create creases in the piece and they will slightly stay there even after the piece returned to it's original shape. Those creases creates a even more believable leather look. Play around with your piece and you'll see.