..... and whilst its a good idea to wash fabric first, I've never found that viscose has shrunk.
it shrinks like the dickens.
@Iminei , first, breathe. Viscose (rayon) is just a little more flexible than quilting cotton and has a smoother surface which makes it seem slippery. It's lovely to sew. Just use a press cloth and not as hot an iron as your cottons.
Remember you are the one who said they are really slippery so you've gotten related answers. Peeps are assuming the worst from this fabric in response.
*It can shrink, up to 25%, usually about 8-10%. Lesser if you only use cold water and line dry, more if you prewash in hot and ever might use a dryer. I make a practice of torturing all my fabric before I sew. It prevents bad surprises later and I don't need to baby anything later.
*The Abakan lady must be a quilter. It's pretty common in my area to clip off the corners of cotton before you wash it. I learned it from an old quilter. It also lets you know if fabric is prewashed or not. I clip off the corners and wash almost every fabric I bring home, unless it's on a bolt. Clipping the corners reduces fraying in that it only frays one row before it reaches the end of the crosswise weave. It can't keep raveling on and on. It isn't really enough for viscose which does enjoy fraying. I'd zigzag the ends together.
*yes, it can be a bit slithery but not always. It needs supporting or it can wiggle off grain. Garments hang better on us if we keep the grain line consistent. The left & right legs of your trousers will mirror each other and the lengthwise grain will usually go with the length of the pant leg.
*You need to support the fabric by not letting it hang off your machine, so use the extension table, the bigger the better. While cutting out use a big table, don't let any fabric hang off the edges. If it's too long, the fabric, accordion fold the excess at one end. I use a big board to press it and Best Press to give it a little more body.
* I've not needed my walking foot but it's a good option. I sew viscose pretty much like I sew cotton. You might want to pin every 4-6 inches on your first seam or two. Adjust from there to your comfort level. Since it's new to you I'd suggest taking some of your scraps after you've cut your garment and do some practice seams, buttonholes if needed, etc.
*Take puzzler up on her offer of overlocking. It keeps your seams pretty. Otherwise get friendly with the overlocking stitch on your machine. It takes forever compared to an overlocker and isn't quite as nice but you simply must finish the seams with viscose. French seams are a good option to use where possible.
* Keep breathing.