phoenix - what are you using to treat the ezcema - might be that you need to resort to a full on ezcema cream til it settles down, and as much nappy free time as you can manage?
When DS had really bad nappy rash, which was only 1-2 times thats what we had to do after trying everything natural. Then when it settles started again.

I agree i didnt like microfibre against my DS bottom either, but had some boosters that were m/f but with a softer sherpa or fleece topper on one side.