Extremely fast. Back in the 80's, I interned in an engineering department. They were just starting to computerize everything - that was supposed to be a large part of my summer job. On the first morning, "have you ever used Symphony?" "No." "How about Lotus 1-2-3?" "No." "What spreadsheet software have you used?" "What's a spreadsheet?" 2 weeks later, I was the plant's expert. 3 weeks later, I was debugging software written by the "expert programmer" who had been flown in from the company's headquarters to get some custom software working at our plant. (He failed; I succeeded - on a lunch break.) 4 weeks later, I had finished what they thought would take me 3 months.
Our school switched to a new brand of software for keeping track of grades, lessons, etc. I was selected as one of the faculty to receive special training so that I could teach the rest of the faculty how to use it. I skipped the training; spent a couple hours playing with the software, then trained the rest of the staff, answering questions that the formally trained trainers couldn't answer.
I bought a tractor 2 years ago. Never operated one in my life. No problem there. (Wife still can't operate it.) Operating it isn't much though. It stopped running well one day. Never touched a carburetor in my life. Tore it apart, found the problem, fixed it; and can now explain how my carburetor works. Good thing, too, because that problem recurs; permanently fixing the source of the problem would take way more effort than tearing apart the carburetor once a month. Speaking of which; I should get my butt back outside and finish getting my hay elevator working, and find the coolant leak in the tractor.