Been picking at these for a bit and kind of just smashed all the info together. The game has a lot of menu paths and quirks. I tried to highlight some not so obvious but very useful things that can be easily overlooked, all in one handy spot.
TRAINING
In the training menu go down to the stage select. Left/Right will let you cycle through each stage so you can practice them specifically. BUT if you press "Shot" [z] it will cycle through bosses, letting you practice the mid-boss, stage-boss and even the TLB (if you have the right difficulty selected.) Practicing the bosses divorced of the stress of the lead up can make a huge difference, I highly recommend giving it a go.
INPUT
Mushi has 2 shot buttons and rapid fire settings for tapping techniques that can be a little difficult to internalize at first. Turning on input display will show a graphic of the arcade control panel that animates for each button and can give a lot better idea of what is actually happening under the hood. To turn it on go here (make sure to adjust the location if you rotated the monitor so you can see it.)
Options > General Screen > Input Display > Show 1P : ON
REPLAY
At the end of a run the game will ask you if you want to save a replay. Say yes! Watching your own replays can make a huge difference in realizing mistakes you are making that are hard to spot in the heat of the moment. Replays have some basic playback controls that some may have missed. You can't skip stages, unfortunately, but max fast forward helps.
"Shot" [z] --
Play normal speed
"Full Auto" [c] --
Fast Forward (Press multiple times for up to 5x)
"Shot Change" [v] --
Slow Mode (Press multiple times for up to 5x)