All I can find online is instructions for the three bath. They certainly don't have a "pre-blix" or the like, though there is a rinse.
I know it's heresy but when the three bath kits came out I compared a small (1 quart, I think, in those days) 3 bath with the 6 bath Unicolor I had been using and actually preferred, by a small margin, the results from the three bath. No one said anything about longevity, and I do still have some of the slides and they are fine. I switched to three bath when I used up the last of that 6 bath since it was quicker and easier and I actually preferred the results (slightly.) I don't remember enough of the details to tell you why.