I struggle with similar problems. I find I spend more time preparing to do something than I do actually doing it, or the techniques I use with study are very inefficient.
I’ve been trying to find some helpful sources of advice recently, and came across this article. While this article might not be overly helpful with prioritising workload, the author might well be a very good source of information. I found the forgetting curve very helpful, which makes me think he has a lot more useful advice.
I looked into the author, Doug Puryear, who is a Psychiatrist who was diagnosed at 64. He talks a lot about his own difficulties with studying when he was going through med school. He has published a book with a section on studying. I have just ordered it via snail mail. Unfortunately the kindle version isn’t available for me in Australia.
Might be worth you having a look though, perhaps his study section though, perhaps it will help :).