Adjust bracelet to target wrist size/shape, because once the 2nd layer is riveted on, you will have limited adjustability.
Texture or stamp the bracelet and/or mustache blank if desired. I simply scrubbed both with steel wool to eliminate minor scratches, and give a nice sheen.
Use bracelet bending pliers and/or your fingers to bend mustache to match the curve of the bracelet. To prevent snagging when worn, fit it as close as you can, especially the tips.
If necessary, smooth some sections of the mustache with a nylon or rawhide hammer. It can be helpful to hammer on a curved oval or round template, such as an oval bracelet mandrel or a soup can.
Apply a small dab of Renaissance® Wax with a soft cloth, to the bracelet and brass mustache. Let it dry for a minute or two.
Mark dots on the brass blank where you plan to punch holes. Are all 3 dots far enough placed where they will securely rivet to the copper bracelet?
Punch center hole in the brass blank. Set brass blank on copper bracelet. Use a fine-point marker or center punch to mark the first hole for the copper bracelet. Verify that the dot is centered, and that all 3 spots will truly work. Punch the first (top) hole in the copper bracelet. Punch remaining 2 holes in brass mustache blank.
Choose a rivet the right length. It should protrude 1-2mm from the backside.
Use reverse riveting accessory to set rivet.
Straighten mustache if necessary. Carefully punch second hole in the copper bracelet (through the hole in the brass blank).
Set the second rivet with reverse riveting accessory.
Punch the third hole and set 3rd rivet.
Touch up any scuffed areas with steel wool, and apply another protective coat of Renaissance Wax to the mustache.