I use the felt as is. I prefer to keep any paste away from my strops. I would imagine felt would work well for pastes though, just not my preference.

For pastes, I made myself a paddle strop of sorts, using strips of denim. I cut up some 8x3 strips of it, attached magnetic tape/roll to the back of it, and another onto the wooden paddle. This way I can swap out the denim pieces which have different pastes on them. Have one with crox,irox, and TI paste. It works pretty well and only cost about $5 for the piece of wood that I made into a handle... and an old pair of jeans...