I have tried them all, and the MTH smoke fluid produces the highest volume of dense smoke. However for several years, I have been making my own smoke fluid by cutting baby oil approximately 50% by volume using a commercial smoke fluid. Why baby oil? It is mineral oil, and a 14 fluid ounce bottle costs about $1.
I do not wrap the wick around the resistors in the smoke unit. Instead I use Tiki Torch wicking cut to fit into the fluid reservoir. I fill the reservoir with wicking to its top, so that it contacts the bottom of the resistors. Then, in lieu of 20 drops, I fill the reservoir with as much smoke fluid as it will hold. Typically about 1" of fluid in an eye dropper fills an MTH smoke unit reservoir I stuff with Tiki Torch wicking.
Here is the result. It's a Rail King NYO&W Mohawk accelerating out of town.
