hi, just bought some jblast supafine grit from FYFFES for my sealy grit blaster (the one that comes comlete with a grey plastic bucket and gun. Is this good for cleaning rusty bodywork? I intend to use my twin cannister filtermask when using it but are there any problems I should know about? Do you have to keep the grit very dry or would it be ok to keep it in the bag in the garage once opened?