Your mic will look better with a nice cover.
We'll cut holes out of the heads, and cover them will speaker grill cloth.
Marking them is optional, but a good idea. You want to leave a strip all the way around that is slightly thicker than the shell of the drum. (if you cut out the whole head, the ring will just slip around the outside of the shell) The strip of head sits on the shell, and the rim keeps it tight.
To help me make a nice smooth cut, I used a washer. The difference between the inside radius and the outside radius of the washer was a little more than the thickness of the shell.
With the metal ring of the head facing up, set the washer flat inside the head, against the ring. Put the tip of the knife inside the washer. The washer will roll against the ring of the head, and keep the blade at the right distance.
Place the drum head "donut" on a corner of your grill cloth and cut out a square just a little larger. Then cut off the corners.
Take a needle and thread and sew some temporary holders in place. Connect each of the eight points to the point across from it by tying off the thread. This will temporarily hold the fabric while it is sewn on.
Take more thread and stitch around the edge. Roll up the cloth a bit to give it something to hold onto (grill cloth is a loose weave). Only stitch the cloth on the back side of the head, _not the front_.
This stitch is similar to the way you would make the webbing of a "dream catcher." NativeTech.org
has better instruction on the technique. For each stitch, instead of going around a ring of vine or metal, you stitch through the grill cloth. This thread won't really take any tension on the cloth until you get half way around the circle. When you make it once around, overlap a bit. Go back to the beginning, and tighten the stitches by pulling the thread with your fingers. You should be able to stretch the cloth a little and get it nice and even on the front side.
Then stitch a second round. It is fine to tie off the first round and use a second piece of thread. This time stitch in between your previous stitches, stitching around both the cloth and the thread of the first round. Tighten the second round, and tie off your thread.
Check your work. The front face should be nice and even, and the cloth should overlap the back side of the metal ring. When all is good, you can cut and remove the temporary thread on the crossing over the middle.
Repeat this step for the second head.