I read that alternate picking economize to up to half in speed, is this true,and what about doing it without nails?cause i still not grown them enough to reach strings, and whether it is a must tool? thanks.
"Alternate Picking" refers to using a pick, not fingers, to play the guitar.
The technique is this:
One down stroke followed by one up stroke. Did you check out the practicing links I sent you? The whole technique is explained there.