Hi! I think “exercise” is the wrong way to think about issues like this. In general, if something isn’t working, that means the motion you’re making might not be working. What is the motion you are making currently? And what about it isn’t working? I think those are more helpful questions to ask.
In this case I actually think this is a pretty sophisticated question, and one we haven’t properly addressed yet. In other words, what motion is used for a sweep embedded in an alternate picking line?
Well in Cascade, there’s this example:
https://troygrady.com/seminars/cascade/clips/mixolydian-medley/
Unfortunately when we filmed this we didn’t get a good shot of the forearm. But I played the same thing a couple years later for the Pickslanting Primer and this has a much clearer shot of what’s going on:
https://troygrady.com/primer/getting-started/clips/pickslanting-primer-intro-lick/
It looks like the alternate picked notes are wrist + forearm, and the sweeps looks like mostly just wrist by itself. You can also see a fair amount of rest stroke during the sweep. In other words, the picking hand actually stops moving when the pick hits the next string, waits for the fretting hand to catch up, then starts picking again. I can tell you I am not aware of any of this when I’m playing, and even when I’m looking down at my hand while playing. It’s just a thing we can see in slow motion.
To make matters more confusing, there are probably other ways this can be done. There are players out there like Yngwie who appear to use finger motion for sweeping and less or no finger motion when alternate picking on a single string.
Lots of options here, no single “correct” way. I’d choose whichever one is most similar to what you do currently. If you want to work on rest stroke type sweeping, take any phrase with sweeping in it and see if you can get the stop and start type motion of the hand happening. If you can get that working by itself, then try introducing some single-string alternate picking into the phrase to see if you can get them both working together.
Edit: Here’s a Talking the Code clip that might be helpful also:
https://troygrady.com/channels/talking-the-code/combining-alternate-picking-and-sweeping/