Compression garments - help!

Hello!

I'm having vaser lipo on my thighs and knees next Friday and have had a nightmare with compression garments! Managed to get one to fit (it's going to be horrid trying to take it on and off though, esp if I'm sore!) but am just wondering whether you wear knickers under or over it, and if people have two - one to wear and one in the wash?

Thanks!
Laura