I have a dress that's a very pretty style and colour (and a nice make) but unfortunately it's polyester and clings terribly to my legs. It's meant to be quite a big skirt, but just sort of moulds itself to me... It also has a crossover bodice that shows off my bra unless I sit up very straight.
Despite that 
I really like it. I'm going to put a button on the crossover to sort the falling open issue, and then I thought wearing a slip would help although it makes me feel about 70.
It's to stop it sticking rather than for shaping, and needs to be quite long - so would cotton be best? I don't know if two layers of polyester would just stick together? I have a waist slip, but it's black and quite short (it was bought to go under an unlined skirt) so no good for this.
Thank you!