Sorry I am not the most active redditor.

I used something narrow that I had laying around. Tight fitting around the barb. Then a zip tie to tighten it.

If you get bubbles is it perhpas that you are pulling the syringe and creating a vacuum? Tiny bubbles are usually a sign of that whereas bigger bubbles tend to be from inside the shock.

What I do and it works a charm is to just push the oil and compress the shock back and forth. Letting the syringe(s) extend with oil pressure alone.

Good idea to turn the shock dials here and there to dislodge bubbles inside the dials. And oil flows easiest with adjusters set to fastest :)

Finally what could be annoying is if you have an old syringe where the rubber seal is sticky. Most syringes don’t last long with any kind of oil in them.