There are just a rare few guitarists who've developed finger-picking skill to rival a flat-pick. Personally, I've spent years on finger-style without touching a pick, only to pick one up and find I'm still faster and more precise with it than with my fingers. Some guitarists will hold their pick between some of their fingers while trying to use other fingers, which I think is self-defeating; and some will even put their pick in their mouths, which wastes time and is most disgraceful. In an attempt to effectively enjoy the best of both worlds (of pick vs. fingers), seven-string jazz guitarist Steve Masakowski invented some kind of folding thumb-pick which years ago he told me he'd show me if I came to one of his performances, but I haven't heard of him performing in California. I don't know how his invention works exactly, but I invented my own solution that works really well:
First, I should mention that it's worthwhile to try a flat-pick. I recommend putting on a Herco Flat Thumb-Pick, holding a normal flat-pick exactly as you would when playing, tracing the normal flat-pick onto the Herco Flat Thumb-Pick, and cutting the latter to exactly simulate the former. Test it and when it's perfect round the edges with a file. If you do this right and grab onto it as you would a flat-pick, it can feel and function almost exactly like a flat-pick, but you can also let go of it and enjoy the freedom of all five fingers.
If (like me) you want more, like the options of deeper tone from the flesh of the thumb, the option to slap chords with your thumb, and the option of switching in and out of having a true flat-pick at any instant etc., I recommend one of my guitar inventions, the Spring-Tethered Flat-Pick:
How to make it: This is seriously easy. Acquire some kind of ring that can be worn at the base of the pointer finger. I used a large plastic thumb-pick. Super-glue the end of a spring from a ball-point pen onto this ring. Super-glue the other end of this spring to your preferred type of flat-pick. (I recommend filing the plastic surfaces that you glue to roughen them up a little bit beforehand.) Put it on and carefully adjust the spring until the pick hovers out of the way of your finger-picking, but within easy reach of your thumb and in just the right position that when you grab it it's exactly where you want it between your pointer finger and thumb. Practice a bit and pretty soon you'll be switching back and forth thoughtlessly.