Does gym work help paddling, the answer is yes most defiantly, the thing that should never happen is a gym session should never take the place of a paddle session if time poor.
I believe know one should do gym unless they are paddling 3 times a week, this may have to change if you can't get to 3 paddles a week. I think your gym sessions should tie in with the timing of your racing calendar. So if you are in your off season you should look to get some strength work done, reps of say 6-8 maybe 4 sets. Then when you have reached your peak strength look at some endurance strength reps of say 15-20, repeat this cycle every 5-6 weeks. What you should see is that over time your endurance strength should increase from the strength work you have done.
I like to focus on a lot of motion exercises that makes you twist and use the whole trunk, I like to do exercises that you use a balance component. swiss ball, standing on one leg these types of things. You can never get away from the trusty chin up, paddlers greatest strength test.Exercises involving cables are always better for safety as dumbbells done wrong can cause serious injuries. I like to always back off the weight and do the motion correct rather then do heavier weight with the wrong technique.
Exercises I do are chins, bench pull, core work, dumbbell pull ups and lots of motion exercises, my gym session go for between 45mins-1hr they are always hard and fast, don't be frighten to mix up your sessions.
Enjoy it don't make it I MUST DO GYM.
Hopefully you will improve your paddling and if you need any help with anything remember I am here to help you.