Thinking about getting house ac unit replaced and using current hvac for my garage/shop. I know nitrogen is typically used in hvac for brazing copper line sets and for pressure testing. Can i use my argon/co2 mig mix for the same?

Could i use helium also purchased from wal mart that is used for ballons? I actually read helium is even better for leak checks.Because the molecules are smaller.
I guess my only concern are if these gasses are "dry" enough.