This is what I went through as a total noob. Might help
- v cut is a must. it not only prevent potential blockage, but also helps with increasing the air pressure going out
- sealing at the bottle cap makes a big difference. after washing for few times, I might not re-assemble it back completely sealed. If you hear "hissing" sound while squonking, you have a leak at the cap and will have hard time pushing juice up.
- either "push-push-push" or "push~~~" works. For most part, 4 - 5 second gentle long squonk works well. However, for PG juices, I found that 4 - 5 quick squonks (without any lag between) works pretty well.
- lastly, to ensure I am not building any negative pressure in the bottle, I blow on the drip tip while covering the air hole. This injects air into the bottle and creates neutral air pressure. If you see bubbles in the bottle while doing this, you had negative pressure.
I tend to over analyse stuff, so all these might be over the top.

But I have been able to suck up the last drop from the bottle without any squonking issue so far.