First thing, know the nature of your beast.
GG isn’t going to require the same physical input style as sf, etc.
For some, it takes a bit of time to readjust their internal sense of timing to the game they’re playing, too. To the rhythm of it.
If you’ve forgotten how to ride the bike, fully…
First thing, readjust yourself to your input device.
Recall/don’t forget how your movements flowed on your controller.
Then try to look for your memory aids. What helps you remember what to do in order to follow up whatever sensory input you’re receiving. (much like seeing a jumping cross up mk from a ken in sf4, you can draw from a pool of what’s possibly coming next with relative success)
Once you get your memory aids back in swing (visual/auditory/tacticle cues, etc) it’s usually gravy, unless your motor skills are lacking since you’ve last played.
One step after that is to readjust your motor controls to that internal timing or rhythm.
To get your wrists/fingers working in concert with your thoughts.
If you’re just slow on the input…
Radial movements on the wrist can be exercised easily enough, stamina and strength can also be worked on, so you don’t get slower after fatigue.
You’ll also probably do fine with some sort of forearm exercise that maximizes the pronation and supination of your forearm (basically the flexing).
That will also result in quickening of the wrist, too. Drummers swear by it.
Then just practice your rotations/movements on whatever input device you prefer.
If you’re just forgetting the moves or theory, play a better, more memorable game
(personally, if I can keep on top of rhythm, my motor function, and theory… it doesn’t matter what game I’m playing as long as I remember what the moves are, and what every attacks look like in my head. It definitely pieces together from there. I keep this shit in mind when going back and forth from fighters)