alecrmyers, the easiest method is to get something like you suggested, I believe it was 3mil tape, and just have it arranged so that the print receives the tape, and the negative film rides the rails. No top rail no bottom rail. It will take extensive cleaning after each use of the motorized roller. When I start doing high volume work or have a budget because it's fine art or commercial assignment/commission, I'll hire an assistant.
Just for clarification, the process I’ve been working on most recently and with which I’ve had the most success doesn’t use rails at all. I’ve previously described it as a “contact” process, of which one advantage is that the (cheap) rubber pressure rollers in a laminating machine work well.
If you’re trying to emulate the Polaroid process exactly (I’m not) then you will need rails and finely engineered rollers like the chrome ones you’ve sourced. The bearings for the rollers and the carriage for the bearings might need suitable upgrades too. So that’s why I’m curious and keen to know how well you get it to work.
https://archive.org/details/photographyitsma001646mbp Neblette touches on coating in the chapter on diffusion transfer but doesn't say much beyond neutralizing any residual reagent and protecting the print from atmospheric contaminants.
Based on what we do know my guess (noting that I'm definitely not a chemist) is that the acetic acid is present to neutralize any residual processing fluid and the zinc acetate is there as a sulfur sequestrant.
I'm thinking a test solution would be to use an airbrushing tool and spraying on the msds listed chemicals, then when that dries, spray on from a spray can some sort of lacquer.
I am fascinated by your efforts and the results of your exploration into this process! I am a new member and was looking for information on making paper negatives. I'm now thinking of the esthetics of your process in making original artwork, and using larger cameras, like Polaroid once did. Have you tried lens filters to improve the contrast of your images? I once read that a yellow-green filter much improves the tonal vales of a Ilfospped negative in daylight. The ISO of 3 was recommended as a starting point.