Try playing a few maps with triples and doubles. If you keep your middle finger curled or just gently resting, it'd be a good idea to stop that and try keeping it ready, and try to just pressing z and x(or whatever buttons you use) as fast as you can during breaks/pauses in songs. If you play CtB and also use the default Z & X keys for playing then I suggest do the same during breaks.
If you use a mouse and you find the other way a bit difficult to keep ready you could try using your first mouse button and the 2nd keyboard key, it's faster if you practice it but it also makes it harder to move your mouse and it's more difficult to get rhythm... I was trying both earlier on some streaming maps and found Z & X more more efficient. But be warned if you have a cheap mouse then it's going to wear it down extremely quickly, I have mouse issues because of osu but that makes my mouse buttons stop working for a few weeks until they magically start working(horribly) again. But I have a very cheap mouse, so I have to try clicking the right mouse button about 5 times to get it to actually click, sometime I have to slam on it.
But yeah, just try tapping Z & X. Quickly during breaks helped me with stream speed, control, timing , etc. I honestly learned to stream in no time doing that.
Hope this helped:)