Using clear monofilament thread and a #4 – 2/0 short shank hook, tie in a tail of white Super Hair mid-shank. Make sure to taper the ends of the Super Hair by pulling the center strands out to longer lengths before tying it in. Take one or two turns of thread under the tail to cock it up at a slight angle.
Cut off six full-length strands of Flashabou and fold it in half and cut it so you have 12 strands of half-length Flashabou. Stagger the ends of the flash and fold it in half. With your thread just in front of the Super Hair tie-in point, hook the loop of Flashabou (formed by folding the flash in half) under the hook eye and tie down with the clear thread. This should put equal amounts of flash of varying lengths on either side of the Super Hair tail.
Prepare 2 bunches of Wing ‘N Flash, Angel Hair or Lite (Long) Brite for the body, a light color for the belly and a darker color for the back. The two bunches should be prepared so that they are longer than the length of the tail plus about ¾” – 11/4”. The bunches should be pre-tapered so that the thickest portion of the bunch is at the tie-in point (just in front of the Super Hair) and getting progressively thinner towards the tail. The easiest method to achieve this taper is to PULL (not cut) the material from the hank and then deal with the material in your fingers. Take any excess material and pull it from the bunch. Realign this material in the area of the tie-in point. Repeat until the necessary taper is acquired. Additional material may be need to gain the proper thickness and taper. Conversely, you may initially select too much material and need to remove some. Practice is key. Your first Mushmouths will probably look horrible, but fish well. Most people find it much easier to produce a finished-looking fly after six or eight attempts. It is critical that you prepare your Wing ‘N Flash bunches ahead of time as you want to tie them in while the Softex or Soft Body glue is still wet. Apply a liberal dose of Softex or Soft Body one-part adhesive to the Super Hair / Flashabou tail along the entire shank and PAST THE BEND. I find it easiest to use apply the glue with a bodkin.
Tie in the light color bunch of Wing ‘N Flash underneath the shank just in front of the tail (about 1/3 of the way back from the hook eye) while the glue is still wet. Take a moment to take the fly out of the vise to equally distribute the bunch of Wing ‘N Flash on either side of the hook bend. It is far easier to do this now, before the glue has set, than later. DO NOT TRIM the butt ends of the bunch.
Tie in the darker color bunch of Long Brite on top of the shank at the same spot as the bottom bunch (about 1/3 of the way back from the hook eye) while the glue is still wet. DO NOT TRIM the butt ends of the bunch.
Advance the thread tight to the hook eye, taking care that the dark color stays on top and the light color stays on the bottom. Comb through the bunches (both behind and forward of the hook eye) with a bodkin to remove any snarls that may have formed when pre-tapering the bunches.
Apply an additional liberal coat of Softex or Soft Body around the exposed thread wraps and along the back PAST THE BEND. Apply a small amount of glue along the belly fibers.
Fold back the remaining Wing ‘N Flash / Lite Brite bunches and tie down. I typically reverse and tie down the dark color first to prevent any spillover of the dark color to the belly. Whip finish. Squeeze and stroke the fly until the desired shape is acquired. Clear the eye area of any random filaments of flash as they will make the epoxy application messy and difficult.
Apply eyes, cover with 5-minute epoxy and let dry on a rotating wheel. You’ll find it easier to apply the epoxy if you let the Softex dry before application. I can typically apply epoxy to six size 2/0 Mushmouths when moving quickly. Larger flies and eye sizes will only let you do two to four flies per epoxy mixing. Smaller flies and eye sizes will let you do more per mixing. I do not use 30-minute epoxy for this task as it is less viscous than 5-minute and tends to bleed into the belly fibers thereby reducing the gap.