Depending on how in depth your Tech pack needs to be I would suggest going out and buying a couple cheap samples. Take these samples and deconstruct them along their seams so you can better understand the overall patterns and seams.
Also when working on softgoods be sure to have images/views/2D drawings for all of the sides as well as dimensions for the important stuff.
The samples will also help you understand materials as well as going to a fabric shop… just remember the higher the Denier the “rougher” the texture and denser the fibers. With that said, 600D poly is not as strong as 600D Nylon…etc so keep in mind not all fabrics are equal.
A great resource to order a plethora of cheap samples is Seattlefabrics.com