Welcome !
There are a lot of drills you can do, but before getting too deep into them, I have to warn you:
What will seem "logical" to us will seem so foreign to you. Keep the following in mind:
Your stroke will take less than 1 second to complete.
During that time, you will have to concentrate on about 15 things.
In my experience, it is not possible for a human to focus on 15 things when starting out, and even less so when worrying about balance (and I admit, I have never tried teaching surfski paddling to a non-human).
First and foremost: your best bet, to save a lot of time, is to find a coach.
Second: video yourself and place it here so that people can help with the most obvious problems.
Third: work on the worst aspect of your stroke first, and if you are unsure, here are some very common mistakes:
Catch:
The beginning part of your stroke is by far the most important (I believe ever one will agree).
Since that seems to be the case, set yourself up for success: SLOW DOWN.
At first, this will be difficult, but after slowing down tremendously, you will be able to work on your balance and on your stroke.
For your catch, you will have a TOP hand and a LOWER hand.
The top hand should not be above your head, and shouldn't be below your mouth.
In fact, top hand should be close to your ear at the start of your stroke.
Start with that, with a good and solid rotation.
Remember, you are working not he catch… spear the fish and then apply power… and then pull out your blade before you think you should.
Think of the stroke as something that you will never be doing perfectly, but that you will enjoy trying to reach perfection over a 20-year period. It's quite fun, because you will constantly be improving.
The catch alone has several drills available to merely help. I'd say work on the above first, and then worry about the rest.
ENOY !
Ludovic
(Brittany, France)