1) D R R R ... after practice, try to contact the follow-up r for a long time, and practice vital capacity first.
2) Then, every time I get up, D is pronounced softly, and slowly it is just T R R R ... In this way, the vocal cord vibration of D disappears at first, and T is very light.
3) then, change t to light e, which is almost inaudible. That's about it.
Remember, you should lengthen R at first. When D can be light, R will not be long, but you should experience the feeling of changing from T to R, and then you can directly find the feeling of Lickitung's vibrato.