Hi, I have not used any picks yet. I just keep a good set of fingernails on my right hand. Going from guitar to ukulele I found that I wanted to grow the thumb and index nail a bit longer. Aaron Keim has a video on using finger picks that you might want to check out. Definitely can make for a louder sound. Taimane uses a “Herco” thumb pick for some of her really fast tremolo picking. The “Ukulele” magazine that just came out has an article on using a flat pick.
thanks, Ron