I was looking into cross string trills (using the picking hand) because Bourree has them in a couple spots and they sound super cool! (More piano-like then hammer on, pull off trills) And yes they sound just as awesome on ukulele!
The only problem is the majority of videos show an advanced 4 finger approach which is REALLY difficult (aka impossible..) to remotely pull off.
Denis Azabagic is teaching a guy new to the concept, and shows him this beginner friendly way to do them.
Fast forward the video to 15:24
This isn’t something you can add to everything but it’s a really neat sounding thing, and not impossible!!