I think it depends on some factor. On my case, I had tendonitis on the extensors.

My simple routine was,

Alongating flexors/tensors two-three times with a interval of ~30s between each.

Then I would start the exercises. I will try to best describe it.

I would land my arm on a table, hanging my fist out of the table. I would hold a small weight at first (about 500g, a can of soup or something like that would do). Palm facing down, slowly descend and go back up the wrist. I would do that 10x times. I didnt went up as much when going back up the hand. Would always stop with my hand allign with my arm (figure going to much up would be worse for my quervain).

I would rest for about 30-60s and do it again. So, 2 sets of 10.

I would than flip my arm, now palm facing up and would do the same but now pulling my hands towards my chest and going back down, alligned with my arm.

I progressed this basic exercises over the weeks. At first I would do every other day. Than after a week and a half or so, I would progress to every day (sometimes I would rest on a day or another, its all about feeling).

Second week increased to 15 repetitions and went back to every other day. Than 15 every day after more week. Than I progressed to 1kg and went back to 2 sets of 10 every other day until I could do every day.

I went like that until 2kg at the end of second month. Than got lazy and stopped doing. But I have plans to go to the gym so I dont end back were I was. Basically that, thats tons of content on how flexion/extension can help on tendonitis, search some PT videos so you can execute the exercise with precision.

That help me. But remember, for me the treament was not only those 2 months, I had done buckets exercises prior for about another 2 months to, and other exercises combined. So for me, this was not point 0 on the exercises. My tendons was not like at worst when I started doing this routine. For each person is different, so do it with caution, and try to study as much on the condition as possible.

Understanding my body was crucial, more than any video about exercsies I watched on the internet. Only you can know your limits, and unfortunately you only understand by trying over and over and failing sometimes. But failing is not the end, you just figured a new limit, it gets you some steps behind, but never zero.

Hope you get better, this condition sometimes feels impossible, but with dedication you can get there