Quick tutorial on “how to do bush/trees ymaps for RedM” without any special tool, you just need to make it all manual and “take it easy” because it is a lot of work and time…
For trees you must do a separate ybn collision for each one.
Helper for rotation conversion between Euler Angles & Quaternions to find the Rotation Matrix degree:
https://www.andre-gaschler.com/rotationconverter/
Good luck!