I'm not a technical trader (so I have no opinion on resistance levels or a short-term short), but I've got to believe there are better short candidates than CMP. I would certainly not buy long term puts on CMP. In fact, I've sold several of them.
CMP has a strong and sustainable foothold in one very stable market (salt) and one growing one (SOP). Shorts could get crushed if SOP prices stay high and volume picks up. On top of that, it's a well-managed company that has been de-levering nicely for a few years.
If you're bearish on ag (I'm not) why not short MON or POT (I'm long MON common and short Jan 10 puts)? If you're bearish on road salt then I guess LT-puts on CMP are your best bet.