When a layer's mode is set to screen, you can paint with solid colors, and it makes it look more like you're using the dodge tool directly on the layer. The bonus is that you can use smudge, etc. on what you paint, without messing up your base texture. Screen brightens, multiply darkens. That's the basics. You paint with shades of grays/tinted grays to vary how dark or light it makes it. Pretty simple, and very useful.
I find it's best to have a reference when painting cloth wrinkles. You'll have a much better idea of what to aim for and where to put things if you have a real-life equivalent to look at as reference. I had this image (above) open on my secondary monitor while I painted the wrinkles in Photoshop.
I start out very messy. Scribbles to lay out my plans. You can also use this as a quick way to check to see if things are going to look correct in max. Get down the basic idea first, save, check 3dsmax and if something's not right, you haven't done too much work yet, so its not such a big deal to go back and change/fix anything.
Use darker tones (like a dark gray-blue) on your Shds (multiply) layer and be afraid to vary it some. Pick a lighter shade of dark blue-gray for some details, and add in darker shds in bigger wrinkles.
Then I go in with the Smooth tool and blend things together better. I smooth out the scribbles so that they look like actual clothing wrinkles, save it and preview it in 3dsmax.
So once I checked out my work in max, I found a couple areas I didn't like. I didn't like the wrinkles in the knees or the way the cloth looked on the thighs so I went back and fixed those up.
Then I moved onto the back of the legs. I use a different reference image (same model, just a rear view) so I'd get better cloth folds.
Again - messy quick strokes to lay out my plans and get things to a point where I can check in max to make sure they're lining up properly.
Smooth it out, check max, make any adjustments you need to make. I actually felt that it had slightly too much contrast so I reduced the opacity of the HLs and Shds layers. When you're good and done flatten the image (Image > Flatten Image), apply add sharpen to it (Filter > Sharpen) and save it as a .tga or similar format.
Moving onto the shoes
Open the UV Rendered texture for the shoes and set it up just like the others (set the UVs up on their own separate layer, rename it, and save the file as a PSD). Set up a material in max for it and assign it to the shoes.
Once again, the photo ref you can find will play a big role in getting a good result. With the shoes, I laid down a base from photo ref, but ended up painting over almost all of it, using the photo base as a reference and color palette.
Pretty basic idea - just copy the reference images, move, rotate and scale them so that they're located as close as possible to where they need to be.
Shoes are a prime example of Liquify being super-useful. Go to Filter > Liquify and nudge, push, and pull the shoe so that it more accurately matches the UVs. You'll need "Show Backdrop" checked, in order to see the UVs to match.
Copy the other parts of the shoe into place, use the clone stamp tool where needed and use Liquify to get things into place better.
Once you have the whole shoe covered in texture, check 3dsmax to see how things are lining up. Because of the way the UVs are setup you are going to have a very noticeable seam along one side of the top of the shoe. This is something you'll need to take into account as you continue to work, and when you're painting over the reference images. You'll have to make sure that the exposed edge of the top shoe UVs matches the side that's connected to the rest of the shoe.