I don't like real limp stuff for Clousers for just that reason. I have tried other things but come back to Bucktail because you just can't beat it for Clousers.
If you are going to use whispy stuff you can't go with a traditional Clouser style fly. It needs to be tied in two sections You need to make the front hair only about as long as the hook bend. The rest need to be tied in at the bend and even then you need to either tie in a mono anti-fouling loop, aweed gaurd style anti-fouling deal or a core that will help hold it out from a fouling position.
The flies on the top left and most of the ones on the right are all tied with very limp stuff like glow in the dark spider web and/or Icelandic Sheep. If you look at the Clousers on the top left you can see they are made in the two stage manner I mentioned. I did a small diameter mylar tube to cover the point I did my tie on of the tail.
There are a couple other flies that have a different anti-fouling strategy. Make the whole front of the fly solid. The slider does that, and the minnow streamer has a softex head.
Bottom line, you either need to use stiffer material or a fly pattern that resists fouling. You can't do a straight Clouser with whispier stuff and not get fouling.
One last note, jerky casting seems to foul them worse and more often. I can do a pretty whispy fly and spey casting it not get fouling where I would single hand casting it.