I'm not expert player, but I just wanna give some opinion.
Play hard map, but not too hard. Avoid mashing keyboard without thinking what you should press.
As AH said, finger indenpendency is the most important for this one. I suggest to play a map that had multiple lns pressed at same time, but with simple different release (like had around 4/4 gap release). It's to teach your indenpendency.
Then, you can learn by shortening one ln on that multiple lns (i.e. If they made as 8/4 and 4/4 release, try to play 8/4 and 3/4 release, then 8/4 and 2/4 release, and so on). It's to teach your reflexes.
In the end, use random mod, it will teach your coordination to the max because you'll avoid muscle memory on same map.
Also, such pattern is hard to be played, especially if you're still adapting to vsrg (I assumed from your play). So, slow progression is ok.
Good luck!