I have tried this with both Naphtha and Zippo lighter fluid. They are different chemicals but both work. Nice thing about Zippo fluid is you can buy just 4 oz can and that's plenty. Probably have to buy a quart of Naphtha. Shave about 1 oz of paraffin or wax from one of those partially burned Christmas candles your wife has squirlled away somewhere.. best look for a paraffin candle.wax is somewhat translucent... into an 8 oz mason jar, add 4 oz of Zippo, put on top and shake a little. THEN leave it alone overnight. Next day, you should find the mix has turned semi-solid at room temperature. If not wait another day, and if still not creamy, add some more wax. ( If you have NO idea how much an ounce of wax is, don't worry. you can't use too much because excess won't dissolve.) Wax will dissolve until solvent can't dissolve any more.Excess will settle as clumps. . and that's when it will turn into a sloppy cold cream. I use it like that, because as soon as you put some on your finger, it turns liquid and you just press that into the fly. To transfer to a container you can use while fishing, you can put the jar full (without lid!!!) into micro wave for 15-20 seconds (watch it closely) or a hot water bath... then it goes back to full liquid and you can dispense it without too much aggravation. I suggest you do this somewhere other than the kitchen counter because you are going to spill some and might get some grief about the smell of lighter fluid and the wax all over the place. Clean up any spilled with paper towel immediately before it dries.. any residue will have to be washed off with lighter fluid or lots of detergent and hot towels.
And always keep in mind that you are working with lighter fluid.. and that fumes/vapors can creep across surfaces and ignite, probably making your DYI fly floatant experience a negative one.
AND when you fill your sealable floatant bottle to carry with you, fill it 3/4 max.. if it gets warm it will leak and the naphtha will burn your skin.