When I was working, some of our jobs were structural strengthening with carbon fiber. The resin we used required that we make a paste out of it. You could mix it as thick or thin as you wanted.
This is what we used as a thickener. Cabot Cab-o-sil Amorphous Fumed Silica. It's about $140.00 for a 10lb. bag. The bag is huge as the material is very light. This stuff will get all over everything if care is not taken. If the Carbon fiber was to be painted it had to be 100% acrylic paint. The epoxy we used was over $400.00 per kit. I don't think you want to use that. I would think the Cab-o-sil would work with any epoxy.
If you decide to use this product PM me and I can give you mixing tips. Hope this helps.
Scott L.