I use Bitspower Ehance Multi-Link fittings along with some E-22 12 mm OD tube and Bitspower 12 mm OD tube. Seeing it's easy to pinch the internal o-ring with the acrylic tube insertion, I started using a round Bic pen barrel and run it around in a circle inside the fitting to push that o-ring up into the crevice. After doing that, nothing but a bit of water around the end of the tube OD has been necessary (for me) for trouble free installation.
I tried using Dawn soap on a few o-rings and it worked very well. BUT! A week later (still building) I could walk to the project and pull the tube out with almost no effort at all. That is with both o-rings installed and the lock ring tight. This could potentially be a problem for other than straight runs and if the tube could slide back out the easily. It would appear the o-rings did not grip the tube. If that is the case, it also would not have passed a leak test.
I understand experiences vary, just sharing mine.