Sounds like you are trying to clip the mics onto the costumes.
A Simple strategy for mic placement:
1) Go to the drugstore and buy some medical tape. I prefer the
clear plastic type but any will do.
2) The belt pack goes on the beltline mid back. Have someone sew together some sort of pouch with an elastic and
velcro waistband to secure the belt packs. This may sound weird but... some people sweat a lot. To protect the belt pack it is very comon to
purchase unlubricated condoms and slide the belt pack inside the condom and then place the whole thing in the home made pouch.
3) Run the
line up the back under the costume.
4) Hang the mic over the ear of the actor so that it hangs down about an inch onto their cheek. Position the mic so that it's aiming the right way and place a small piece of tape above the mic cable on the cheek.
5) Run the mic cable over the ear and around the back of the head. If possible use a
bobby pin to pin it in the hair so it can't be seen.
6) Have the actor turn head side to side to establish how much slack you need. Tape the cable to the neck.
7) Have the actor report to makeup for a very delicate touch up to
cover as much of the TAPE on the cheek as possible... careful not to touch the mic with makeup.
EDIT... how high do you have the input
gain both on the baord and on the mic itself?