Check Vibra-Tite VC-3 Threadmate. "VC-3 is a proprietary blend of thermoplastic elastomer resins designed to remain flexible and absorb vibration"; it doesn't harden like Loctite and other threadlockers.
https://www.vibra-tite.com/threadlo...ble-threadlockers/vibra-tite-vc-3-threadmate/
https://www.vibra-tite.com/threadlockers/removable-reusable-threadlockers/vc-3-tape/
About mounting the rails...I've done it myself. I'm comfortable mounting bindings, and I have the tools. The rails don't have a mark for the boot sole center line, so I set everything up on the bench and put my boots into the bindings with the bindings set at the correct spots for the sole length. I transferred the sole center mark to the rails, then put the rails on the skis with center marks matching. Lined them up, marked the hole positions, drilled & tapped the screw holes, and mounted the bindings. On the full length rails I had there were 4 pairs of screws. One pair was fixed; it held the rail firmly. The other three pair of screws were in slots that allowed the rail to move longitudinally along the ski as the ski flexed. Of course if a shop can mount them, great.
Question--does the shop need a different jig for the twin rails (short rail under toe & short rail under the heel) or the full length rail? Likely different jigs, but one might check with the shop before ordering rails through them.