I worked on a  muscle project about 3 months ago - ATPase staining.
I first of all cut a piece of manilla cardboard slightly bigger than the
tissue to be
frozen. This prevents distortion during freezing. I suspended a small
stainless steel beaker of isopentane into liquid nitrogen. I attached the
muscle to the piece of manilla cardboard and then suspended this into the
isopentane for 30 secs. (depending on the size of muscle used).
As soon as the muscle was frozen I immediately wrapped this with Saran
Wrap.
Everything was stored  at -70 degrees C. Just before sectioning the manilla
tag can
be pulled off and the section can be mounted onto the chuck with OCT
Compound.
This procedure worked really well for me. I enclosed this procedure to save
a lot
of frustration . Good Luck !!