In addition to finding out if, or how much, the glaze will run, the test tiles will let you see what the glazes look like without the reduction that takes place in raku process.. There's a good chance that without that step, they're going to look a lot different than expected - and your student may decide they don't like the results well enough to use it on the pieces they originally planned.
Have never tried it, but remember reading somewhere in this forum that skunk hair works quite well. Don't recall who posted it, but they mentioned keeping a bag and gloves in their car, so they could collect such hair from road-kill when the opportunity arose.
I have tried several times but my slip will not release from one section of the mold any ideas of what the issue is I have waited over night and it still stays in that one section
Need more info or photos than( my mold) like what is the form are there undercuts-was the plaster mold dry -has it ever worked before or is it a new mold? is the slip the right stuff. is the mold a solid one or did you drain it out at the right time.