Fleece! We use fleece soakers and longies, and don't have issues. I haven't gotten up the motivation to hand wash/lanolize wool. Ditto EFF board if you're set on wool, they should have some suggestions.
We just started using lovelybums interlock wool cover for nighttime over cricketts fitteds. The combo is working really well I think for my supersoaker.
Re: Recommend your wool soaker
You'd probably have better luck on the EFF board:
https://talk.thenestbaby.com/boards/ShowForum.aspx?ForumID=562
We're not having to do anything beyond an extra doubler at this point, thankfully.