You can use most matt with epoxy. The epoxy won't dissolve the binder which makes it harder to wet out, but you can still use matt and it still works fine. I did suggest biaxial cloth for this reason, though.

Here is a fiberglass repair I did. I replaced a section of a boat stringer. I used 2 layers of 1.5 oz mat and 1 24 oz roven. I used West System epoxy and it wet the mat out just fine. In fact, you can still see the wood underneath all of the glass.