If you don't have the Per*Exp to find rustroot, you're just as unlikely to have the strength/tools/time to find a node via snaking. It takes an incredible amount of mining to find a node that way on aveage. Just going off my experiences in caves, it would take at least 1000 tiles mined on average to find a node like that.
Have one of your guys specialize in exploration and save the perception food for him. It's the best way to do it short of outright moving after you find an unclaimed cave somewhere.
P.S. Prospecting is often confusing. I'll shamelessly reference my guide on how it works
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