Some of
these links might be useful, particularly the third one. Not a sculpting tutorial, but it's pretty useful to see where folds and wrinkles might go. Heck, you can even wrap a sheet around yourself and look in a mirror to get a basic idea of the same. Though at the same time, keep it simple.
For putty, if you buy green stuff, mix in more yellow to make it it softer for longer, which'll make it easier to stroke and blend into clothlike folds. The manufacturers of green stuff recommend 3 parts yellow to 2 parts blue for general sculpting.
Alternatively, see if you can also get a soft, claylike putty like magic sculp or apoxie sculpt. There are two similar
UK products called Cold Clay and aSculpt. Unfortunately I'm not sure what's available to you in Sweden.
Now, personally, I think these can be a little
too soft and fragile for modelling details at wargaming mini scales, without a bit of experience or leaving them to stiffen up some; but they're great if you mix up a little and then mix
that with some green stuff. It softens green stuff and 'loosens' it's chewing-gum texture nicely.
Here's an excellent article about green stuff and apoxie sculpt, and how they are when you mix them together. (And
here's a few more articles to go with it)
Tool-wise, what do you have? Personally, I think most putty-pushing is best with hard metal or wooden tools behind it (and those tools with good, fine edges and points, which unfortunately excludes Games Workshop sculpting tools) but clay shapers can also be useful for shaping and smoothing cloth folds in soft putty. If you haven't heard of them, clay shapers are like paintbrushes, with a wooden handle and metal ferrule, but with a shaped silicone rubber head rather than bristles. Clay shapers are the type with 'extra-firm' black heads - the 'firm' grey and 'soft' white types are known as colour shapers, intended for manipulating paint and pastels etc. 'Colour Shaper' is the overall brand name: other off-brand silicone tools like this are cheaper, but don't have the range of sizes and firmnesses, and may be coloured differently.
Personally, I like a size 0 'round cup' clay shaper for smoothing, and a size 0 'taper' can be useful for marking and smoothing soft folds in cloth. Size 0 taper and flat clay shapers can also be bought with wire loop sculpting tools of the same shape on the other end of the handle. (I.e. a rounded point or square, respectively), which can be handy for the extra push needed from a metal tool, though without the near-knife-sharp edge that a miniature sculpting tool needs. You can at least take a look at them on the Heresy Miniatures site,
here.