You can use any ole' capacitive stylus which just, basically, transfers the electrical impulses from your fingers through the stylus to the iPad's screen, instead of just the electrical signals from your fingers being simply transferred to the iPad's screen directly.
There are, relatively, cheap capacitive stylii OR better made/quality capacitive stylii.
Common capacitive stylii, usually, have fairly large diameter tips, similar to the tip of a finger.
If you want to use something that has a finer point, like a real pen or pencil, the only ones you can use on an iPad 2 model reliably are the so-called "active" styli.
These either use a standard AA, AAA or rechargeable battery that creates a much smaller electrical field around the fine tip point of the stylus than you finger is capable of creating.
These type of stylii, most times, do not require any Bluetooth connection or pairing.
Neither types of stylii use any sort of palm rejection, so you can't rest your hand or palm on the iPad 2's screen while drawing or writing.
Better quality stylii in both categories, for an iPad 2, are made by companies, like Wacom, Adonit and The Joy Factory.
There are NO smart Bluetooth stylii that will work with an iPad 2 because the Bluetooth spec version on a iPad 2 is too old for most of the current, modern smart Bluetooth stylii available.
So, your only options are the common capacitive stylii or the "active", battery powered style stylii.