music and motion

Since i began playing ukulele (18 months ago) i've used the P-I-M-A technique, designating the A-A, the M-E, the I-C and the P-G. Now progressing to slightly more complex pieces i find this can be limiting. If the melody notes sit on the 'A' string i'll simply use my thumb to pick them out, but when melody bounces onto the 'E' and 'C' strings i employ the use of all fingers, however when a quick succession of notes are played on one string i find it hard to play up to tempo.
I stumbled across a classical guitar forum and with this instrumnent it seems fairly common to employ a flameno style picking for quick multiple notes played on one string using typically the 'A' and 'M' to get the job done. This seems to avoid that jerky robotic sound i sometimes get when trying to pick out notes in quick succession on one string but also leave my fingers a bit confused.
Does anyone use this technique to keep movment and flow, or in time will string assigned to finger produce less rigid results?
Aldrine seems to manage just fine getting it done with his thumb alone!
What's your playing style for quick tempo melody notes?

I use PIMA which isn't meant to be a static device (meaning, PIMA fingers should shift down to PIM (C-E-A) or PI (E-A)), so it sounds like what you're doing is mostly correct. Keep in mind that PIMA are finger designations which don't shift no matter which string/s are played.

For one-string picking, it's acceptable to use alternating I M A on one string (or even I M). With practice, this will make you really fast.

I used to play the electronic Mattel Football game that came out in the late '70's. So picking fast with just my thumb isn't too difficult speedwise. For a few classical songs that require fast picking, I like using a guitar pick with a soft hand. To me, it just sounds better, mostly because that's what I'm used to.

Like with most things, it's about practice, breathing, and relaxing. It's also about learning the rules, knowing when to break them, or just doing what works best for you. Some amazing musicians (i.e., Tommy Emmanuel, James Hill, Kimo Hussey...) play by their own rules, each having their own unique style and flair.