e46 is an easy car to make a quick adjustment right at the handle.
you will need a 10mm deep socket, a ratchet, and a small extension 3 or 6 inch will work fine. 1/4 inch drive preferrably.
carefully pry up the leather boot around the ebrake handle, leave it attached to the handle just make room so that you can access the ebrake cables. Now you will see 2 cables with 10mm head nuts holding them against the handle assembly. just simply tighten each of the nuts a turn or 2 at a time back n forth evenly until you get the desired feel out of the handle. 2-3 clicks until you feel the brake engage is usually about right. If you get to the end of the travel and the brake handle still doesnt feel tight then the shoes may be worn or out of adj. back at the wheels, or in high mileage cases the cables could even be stretched. In that case you will have to dig deeper but most likely it will be possible to just make a quick adjustment right at the handle.
Hope that helps,