Hey Fuyu,
I use a flat pick, and my fingers, and sometimes just a flat pick. If I'm playing an acoustic, then I use a thicker pick(1mm or above) to play.

If I'm playing an electric guitar, then I use a thinner more flexible pick.(.63-.88mm)

What matters is what you prefer, like BrokenJera said try out some different picks and find one or two that you like. Practice strumming a chord, and see which one feels most comfortable to you.

Everyone has different preferences, and you may decide later that you prefer a different pick. Tortex, or Jim Dunlop are good, because they outlast most of the others.

JD
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