Go to long stream practice, start from easiest difficulty (120 bpm), and spam it. When you fc it with 95%+ acc and 150 unstable rate or lower (the lower the better, I recommend 100 UR or lower), go to the next 10bpm and repeat. This will build up your control and stamina for streams.
Get a lot of stream maps, make a collection for the maps, and spam them (do NOT retry more than 3 times). This is for speed and adaptation for patterns but doesn't guarantee you much stamina and control.