If you can find the equipment for vacuum bagging, go for it. However, for the rest of us who race, break boats (we all do) and want to keep the weight down...just use nylon peel ply.
You just apply this over your patch while the resin is still wet. It soaks up excess resin and you are left with a lightweight patch with just enough resin, pretty much the same effect as vacuum bagging...with much less effort. I have repaired boats the night before Team Trials and Nationals in a parking lot with this stuff, producing outstanding results. I use this when installing my outfitting to keep the weight down.
If you really want the perfect patch, put a lightweight layer of fiberglass over your patch, use peel ply to get out any excess resin, and wet sand the whole thing to get a perfectly smooth finish. Myself, I only did this once...just to see if it worked. My theory is the friction difference is not going to make a difference until my upstreams look like Tony Estanguet.
You can find all of the materials, supplies and advice you need from Sweet Composites, owned by Davey and Jennifer Hearn. They know boat composites arguably better than anybody in the country. The peel ply can be found here:
http://www.sweetcomposites.com/Polyester.html" onclick="window.open(this.href);return false;. Look for the Nylon product on that page. Your Kevlar, Carbon and combination weave patch materials can be found here:
http://www.sweetcomposites.com/Kevlar.html" onclick="window.open(this.href);return false;.
Besides that, get yourself some West Systems epoxy, rubber gloves, cheap duct tape to mask with, and a dremel to do the fine sanding with in combination with a small hand power sander. Best of luck and welcome to the zany world of slalom.