I found a great tutorial that pretty much answers most questions on making system clothing (It is for SL clothing but works exactly the same way). The author's instructions are given using photoshop but with a little thought you can translate it to Paintshop, Gimp, or whatever program you are using.
There are lots of tips and techniques, hopefully it will be helpful to someone
Here is the link:https://chimerafire.wordpress.com/sl-cl ... ion-guide/
have fun, if anyone has any trouble translating techniques to paintshop let me know I might be able to help since that is the program I use.