I find the washer, even on a gentle cycle is to much agitation even in a mesh bag for small pieces of fabric. I go for the hand wash method for FQs and charms etc. Just toss into a bucket of hot water and touch of suds, gentle swish with my hand I do wash all my fabric before using it. Iron and size while still damp/dry. Mixing fabrics has never been a problem as long as they are of similar weights but this is also not a stedfast rule.
peace :D