I've researched several recipes for homemade gel fuel, all of which require you to spend several hours evaporating the water out of the vinegar. Since I'm looking for something a little more quick and easy, I experimented with reducing the vinegar before mixing with the other ingredients...and it turned out, it worked! So here's my special process for a much quicker concoction.
Pour a half cup of white vinegar into a saucepan and bring it to a boil. I found that after about 5 minutes, it's reduced to just under ¼ cup. This process is imperative - you aren't just needing less liquid, you're wanting less water in your vinegar. It's the same process as reducing a broth when cooking. Make sure you reduce it to at least ¼ cup. Reducing more is better than less.