I often get asked about what right hand finger technique I use when playing the ukulele. People tend to ask this as unlike the classical guitar, where the technique has been honed over hundreds of years and is a well trodden path, with the ukulele it is less well studied. It is therefore much more open to interpretation as to the best right hand technique. The other issue is that there are many players out there who use predominantly just their thumbs for strumming (something you would never do in classical guitar) but still get an amazing sound.
My technique is very influenced by my background on classical guitar. It try and use all the fingers (P I M A) - thumb, index, middle and annular. It is good practice to try and never hit the same string twice in a row with the same finger. You should be able to get a much more syncopated sound by alternating the fingers.
Do I asign fingers to certain strings ? Well, not really. I tend to keep the thumb for the top two strings G and C and if I am missing a strong out I would use I and A rather than I and M. I try and come across the strings at a slight angle (towards my elbow) rather than straight up as I believe this gives a slightly better tone. I am also a firm believer in the use of nails rather than pads.
So, what do I think of players who mainly use their thumbs. Well, you only have to watch someone like Kimo Hussey play, who completely blows me away, and you soon think - hmm there is nothing wrong with that. Benny Chong is an amazing player who also uses his thumb a lot, but mixed with his fingers.
So, where does this leave us. Well for me, it has to be fingers over thumb , but that is solely because of my classical guitar background. If just the thumb works for you, then go for it. That's what I love so much about the ukulele, its still in its infancy and there are so many styles. I love the fact that people are not too stuffy about the way you play either.
I have attached a little video showing my right hand technique on a piece called 'Kemp's Jig' taken from my
book 'Classical Uke'.