Since I had to do the same for our 4Runner, I decided to get this funnel to see how well it worked. I had seen this design in a YouTube video prior, and it pique my interest. Not only did it prevent spills, but it also kept things clean in case you were to ever need to check for a leak. I was sold as soon as I saw it.
The video attached is the process of burping the cooling system in my 4Runner with this funnel. Not only was this efficient, and quick, but it was clean as well. I think I managed to lose 5 drops of coolant transferring the funnel from the radiator to the overflow tank, and that was probably just what was on the outside of the funnel neck.
I'd highly recommend this thing for your next coolant flush. It's totally worth the money, and everything seems to be top quality. It may not be something from the Snap-On truck, but it'll last if you take care of it.