Used the Nettie pot twice. Two words of advice for anyone who might try this. One, it doesn't work if you nose is completely plugged up like mine was this morning. The water just collects in your sinuses growing algae and plankton. Two don't use cold water, I won't go into why I know that.
Definitely always use warm water, as warm as you can tolerate(but not so hot to make your eyes water

), especially if you're that constipated as it'll only help unblock you. I get pretty conjested also during the september hay fever season yet I've never been so conjested that I couldn't get a flow going, I takes more than twice to get use to running fluid thru your nasal passage but like driving a car, it'll get easier with practice. I can only suggest that you stick with it, it will get better with regularity, that being the key.
You might also want to wait a few hours or even til the afternoon before using the neti pot. I'm always my most conjested 1st thing in the morning but tend to clear out after I've been up for awhile. YMMV
Discloser: This has been an unpaid service announcement from your unemployed audio forum A'hole.
Cheers,
Robin