Try Back2Natural Med Ash Brown. The rule with B2N is to get a shade one step lighter than your actual hair shade for best results. You can always leave it on longer or use it more than once to get a darker color if you need to.

My favorite off the shelf hair color is Perfect 10 from Clariol. It's specially formulated to be less harsh than most hair colors, and works quicker (10 mins). It never dries my hair out. Nice & Easy by Clariol is another good one to try. Stay away from L'Oreal haircolor, it will dry your hair out badly.

I always do a "strand test" by selecting a small area (about the size of a pencil) on the edge of the piece at the very back. Mix a small amount of developer with the color 50/50 in a small plastic container. Let it process on the selected hair strands about 3-5 minutes. Rinse and check color by drying the hair. Repeat the above steps if necessary to achieve the desired color depth. Make sure you record exactly how long the color is actually on the hair each time. Add those times up to get your total processing time (example: 3 mins + 3 mins = 6 mins total.)

Put a plastic bag over your styrofoam form and pin the piece down. Apply color starting at the back bottom and work your way around to the sides going up to the top little by little (1/2 inch sections). Apply color to the front and top last. (I use a small 2" paint brush to apply the color, then comb it through the hair.) Be careful to keep the color off the knots & the base at all times. Carefully rinse the color away from the base; base side up, to keep it from staining the base.