I have only ever played with a pick, and I have not been playing guitar for long, but I know mark knopfler uses a lot of finger picking in his songs and I'm wondering if i'll need to grow long nails for this?
Knopfler uses a thumb and two finger, "claw hammer" technique. You can actually do a decent impression of most of his stuff using a "hybrid picking" technique. Use the pick normally, and finger pick with the middle and ring. Nails? That's just a question how you want your attack to sound. Obviously fingernails, fake or otherwise, will have a different tonality than flesh.