Some tips I've learned...
Use NON-iodized salt. The iodine can sting. Too little salt feels like pool water (very uncomfortable) and too much stings.
I found that doing neti pot in the shower made it much easier to get the flow going! I do it at the end of a good hot shower. I turn the water a bit cooler (more to "comfortably warm" than "hot enough to steam my sinuses open").
Also, putting my head in a more upside-down position made getting the flow easier when really congested. This wasn't really possible for me over a sink. Doing it in the shower solved that. Plus, I'm less icked out about it if the solution runs down my face - I'm wet already, so it's no big deal.
Finally, doing the "stage 2", more advanced neti pot technique really REALLY helps me with congestion that the regular flow won't touch. Here's a link:
Do this gently - I've made myself bleed by doing it too forcefully.
Another plus for doing neti pot in the shower is that, in the process of drying off (bending over to get my legs and feet, moving around etc), I sort of automatically get much of the excess solution out! I find that I don't generally have to do anything extra to get the water out.