A moment to discuss color theory,
IF YOU PLEASE
there is a HUGE difference between print and paint, I have done both
in print, you have colors, Cyan, Magenta, Process blue ect,, they are "pure " colors
In paint you have several yellows, one that is a blue cast, one that is red cast and one that is clean
you have blues that are red cast, green cast
you have reds that are blue cast, and yellow cast.
while in an ideal world, assuming you could get a TRUE yellow, a TRUE blue and a TRUE red, you could mix most colors that way. Therein lies the problem, there are no pure toners for auto paint available. The reason for this lies in the fact that the paint is not truly opaque. as a result, the light reflects off the pigments differently. Each pigment particle is ground to a different size for various reasons before its suspended into the carrier. In doing that, the light will bounce around inside the layer of paint and a different color will result.
One important thing to realize when dealing with color, you are not seeing the color, you are seeing the color that represents the frequency of lightwave that is actually being reflected by the paint. the colors of light that are absorbed are everything else in the visible spectrum.
white is in fact the presence of ALL frequencies of visible light in the proper balance, black is the absence of any reflected light. ( thats in pure color theory.)
so, in paint, you cannot mix every color with three toners because of the cast in the pigment, you could come close but not quite do it.
Randy Powells's method is about the cleanest approach I have seen for using auto toners in dope. Personally I just mix what I need, but then not everyone has access to a mixing bench with all the toners on it. Be advised that not all two stage urethane systems are viable for this method, some like Nexus and a couple of the current PPG systems have the clear Urethane binder as part of the bench mix colors so you are not able to leave the binder out ( to be replaced later with Dope)
I would follow Randy Ps brand reccomendation personally if I were to go this route.