Pan Matrix was aimed at the market of advanced color darkroom users - portrait, landscape, wedding photographers and artists. Labs never really embraced it because the busy/successful ones had their hands full making dyes from transparencies for ad agencies (a much more lucrative market).
Pan Matrix was relatively simple when compared to the other methods. Direct exposures were made onto 3 matrix films through red, green and blue filters. The film was available in 14x17 and another larger size - prepunched for registration. You could use a standard B+W enlarger with a glass or oil carrier to keep your neg from moving, expose your 3 mats, develop in Kodak tanning developer and then you're ready to print.
They stopped making this product a few years before they discontinued the entire dye transfer product line. There simply wasn't a market for it.
I've made dyes from negs using Pan Matrix and by making interpositives. With a very good quality neg, you can't beat Pan Matrix, however the separation method allows for infinite control. One of the last ones I made used over 140 sheets of film for all the masking I did on an underexposed neg. Today you would just crank some curves in PhotoShop.