I switched to Dvorak at least 10-15 years ago (and have been enjoying it ever since) so I can't tell you exactly how long it took me, but I'd say to expect to have lower productivity in Dvorak for a month. By then you should be at least near enough to your QWERTY proficiency that the switch will no longer be hurting you.
Advice for learning: Start with basic typing exercises that drill in the muscle memory. Then switch over and keep a keyboard layout visible. Switch back to QWERTY when you need to. When you rarely need to look up letters but still need to think sometimes, switch permanently and try not to switch back to QWERTY.
On keyboard shortcuts: while some such as copy and paste are worse because they involve the right hand, I find many keyboard shortcuts are actually better on Dvorak despite being designed with QWERTY in mind. J and K for instance (think vi navigation) are really convenient. There are a bunch I feel that way about, and that's in addition to other characters used in programming often being more convenient as well, such as brackets/braces and hyphen/underscore.
On fluency: I definitely have a hard time switching back to QWERTY. Funny story: an interview didn't go well once when I had to complete a programming task on one of their computers. It was Windows (I use Mac) with a QWERTY layout! I must've looked like I didn't know how to use a computer. But I'm typing this paragraph in QWERTY and it's doable. Most of what makes me feel slower on QWERTY is just that it's so much less comfortable to type in than Dvorak.
Advice for learning: Start with basic typing exercises that drill in the muscle memory. Then switch over and keep a keyboard layout visible. Switch back to QWERTY when you need to. When you rarely need to look up letters but still need to think sometimes, switch permanently and try not to switch back to QWERTY.
On keyboard shortcuts: while some such as copy and paste are worse because they involve the right hand, I find many keyboard shortcuts are actually better on Dvorak despite being designed with QWERTY in mind. J and K for instance (think vi navigation) are really convenient. There are a bunch I feel that way about, and that's in addition to other characters used in programming often being more convenient as well, such as brackets/braces and hyphen/underscore.
On fluency: I definitely have a hard time switching back to QWERTY. Funny story: an interview didn't go well once when I had to complete a programming task on one of their computers. It was Windows (I use Mac) with a QWERTY layout! I must've looked like I didn't know how to use a computer. But I'm typing this paragraph in QWERTY and it's doable. Most of what makes me feel slower on QWERTY is just that it's so much less comfortable to type in than Dvorak.