I use my nails when they exist. When they do not exist I use picks or get blisters. I cannot use flatpicks - I just lose them inside the guitar. I use medium Gibson, Fender or Rotosound thumbpicks. I had a worn one that I liked a lot, because it was easier to play with, and used to file the tip down to simulate wear - but now I always reduce the pointy bit by setting it on fire and blowing it out v quickly - less effort than filing. Metal picks are easy to make from old cans with a pair of scissors, but a metal thumbpick does not cope with upstrokes and opens out unless supported with the index finger. I find that plastic fingerpicks as bought are better if distorted using hot water and worn the "wrong" way round, ie picking surface = nail side of the finger, but not curved - straight. Richard Grainger always plays with metal picks the wrong way round and I have been astonished for years as to how he keeps them on his hand doing this. I have tried it but I get fed up of the dang things falling off.
End of 30 yrs experience of trying to use picks. I still avoid them if possible.