I only use polyester for FMQ. Cotton is used everywhere else.

Personally I prefer FMQ with polyester thread. Like Jane Quilter cotton is everywhere else. Just be careful to secure your start and stop areas. Some polyesters tend to fray where cut.

I have used it and never had a problem.

I use whatever thread I have in the correct color, except I limit rayon to thread painting because it isn't as strong and my quilts are washed heavily, I hope. I like poly.