Re: Working with mat...
Sall pieces of mat can give you the fits sometimes. That being said.
I like to first wet out the area that you are going to put mat over. This will encourage the mat to stay in one place. Then lay the mat down and start to wet it out. If it is a large area I use a 3" roller and for small areas a small chip brush. Once you get a nice sized area wetted out, start going over it with the aluminum roller. If the area is not wetted out enough the mat will try to roll up with the aluminum roller, if so put some more resin down. And if even if there is enough resin it still seems to stick to the roller a little bit on the first couple of passes, but just keep using the aluminum roller and it will flatten out real nice.
The clumps you saw could have been from the resin starting to gel. However, when using a chip brush to wet out the mat you often bring some mat back into the container in which you have you resin. This makes the resin look clumpy and it is not due to the resin starting to gel.