I learned what little finger-picking I have from the Alan Lomax/Pete Seeger American folk Guitar book (price 5 shillings in the 1960s!)Watching other guitarists you see some who achieve quite a lot by only using the thumb, and others who perhaps use one or 2 fingers + thumb. IMHO you've got 5 digits, so don't be afraid to use them all, and more than one at a time! I've never mastered how to use thumb-picks or a plectrum, I just let my nails suffer !
TB