Mine is an opinion that lacks some experience but...
I have been running a combination of several fuels in my front tank (1990 F-250 7.3L IDI 2WD) including:
Waste Veggie Oil
New(found) and used ATF
Waste Motor Oil
My truck actually runs better and smoother on the above mix than on straight diesel, don't know why/how but it does.
I don't have any "kit", nor do I heat the fluid in any way.
I start on diesel in the second tank, switch to first tank once the engine warms up, and switch back to diesel before i shutdown for the night.
During the day, whenever I have to shut off the truck, it still starts fine on the first tank when I restart it.
I didn't run this way during the winter because I didnt have the truck then, but in winter I'm sure you'd need something to preheat the lines/tank maybe.
Very simple I would think to make your own "kit", how hard could it be? $1,700 for a kit and I only paid $1,100 for my truck so that's not happening. I'll make my own if need be.
I have been filtering all my stuff through stages of black landscaping cloth and t-shirts...probably not the best but the end result for the WVO is a light honey colored fluid that flows like 5W-30. I plan to incorporate some kind of magnet to catch any metal particles in the WMO/WATF and add a 20micron pre-filter into the fuel lines.
and it seems I get as good or better fuel mileage on the front tank than on reg diesel.