[Harp-L] Trying to make overblows sound sweeter

[Harping On]

https://youtube.com/shorts/4pGCI6BCFTU?si=MIYklbLe64a76fXh

I have been trying to soften the harshness of overblows on a sustained note
by kind of lightly bouncing the harp on my lips. It's not really vibrato as
described in the video, but more like tremolo I guess. Has anyone tried OB
vibrato? I have had a go on bending the overblow on and off but can't get
it smooth enough yet.