Could you please advise? I have two questions:

1) Can you tie nods in them for good grip as you can with a cotton or nylon long line?
2) If not, would you know of a supplier who stitches grippy material on it, without much reducing pliability and weight?

Thank you so much for any information and advice you can provide!

I read this previous thread: http://germanshepherdhome.net/forum/ubbthreads.php/topics/74425/1

PS I am heading out in heavy rain with a dog in training, taking advantage of parks deserted due to the rain, but dreading my cotton long lines getting wet and heavy!

you will want betathane for your line (biothane could be ok for collars but it is less "bendy" and can separate and is thinner)... if it gets wet it IS slippery but is so easy to clean. i would imagine you can tie knots in it, but it is kind of bulky and the knots will not "tighten" so they may "move". there are some places i saw that do have the grippy stuff you could get on it but dont know how that would change the pliability or weight of the line.

How about this? I have a few 6 foot leashes in this and I like them.

http://www.dogsportgear.com/58-Gripper-Tracking-Long-Line-Black-ONLY_p_228.html

I have a biothane leash from k9noz and I tie knots in mine just fine. The knots are tight and do not move. I use them, like you said, to get better grip. Hope that helps!

If you do use the gripper line, be sure to wear gloves or you may get burns or cuts if the dog pulls out.
I have a smooth line, my dog is very handler sensitive, so doesn't pull or barrel down a track.
But I've seen injuries to hands with gripper or even smooth lines if the dog is pulling.

Yes, wear gloves! I have a smooth line, and when Mason tracks he pulls and barrels down the track, gloves are must with him or else my hands would be a mess.

Thank you all so much for advice and input! Haven't ordered one yet, still circling and sniffing. I burned through a (cheap) pair of gloves already with my cotton long lines, lol. Tough girl in training but fun. Getting there.