I have not truly mountain biked since the early 90s. I do remember mud being an issue (I grew up in Oregon after all) and Lewis sent along the following hack to help fight crud.
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Instead of throwing away a badly worn tyre, fashion a "crud catcher" from it.
Fancy neoprene ones cost upwards of $20++
A discarded old tire cut to size (using cable cutters to gnaw through beads) and normal scissors. Zip tie it to the suspension arch and upper stanchion mounts. I made this.
All thats needed.
1. Old tyre
3. Cable cutter
4. Zip ties.
Its not pretty, but it works VERY WELL! It lasts much longer than inner tubes. A larger version of the same picture above is available here, and an alternative view here.