Shooting from the saddle didn't take long to get the hang of for me. It's like any elevated stand as far as leaning, bending, or twisting at the waist so that you get proper alignment.
I carry climbing sticks in and out with me so my biggest challenge has been getting up the tree and setting up my platform (3 strap on steps on one strap) quietly.
I've had the saddle for a couple of years but have only hunted out of it a hand full of times. I really want to make the saddle work this year so I've been practicing more in the back yard to get my system down. I'm still figuring out how to be most comfortable in it for long sits. The few times that I used it last year I had a hard time getting comfortable and felt that I was fidgeting way to much. You have to position the saddle just right on your butt or the straps can bite into your thighs. I've heard from others that they sit in the saddle all day, but I still need to find the sweet spot where I can sit for long stretches without moving.
The height that you attach the strap to the tree is important as well. Some like it way up high and others lower. I'm still trying to figure that out too. Knee pads are also a must. I just bought a $5 pair of closed cell foam ones with an elastic velcro strap and they work fine.
Back to your question, I think you can figure all of these things out and be proficient with it in a week or less - maybe a few days of playing around with it.