Petroleum jelly or baby-oil is not the answer. Your hands are going to sweat inside latex no matter what you cover them with.
However, surgeons use a trick by blowing corn starch lightly into an unpowdered glove. This will not stop perspiration, but will greatly inhibit the 'slippage' inside the gloves and keep your hands slightly drier.
Powdered gloves actually increase the amount of sweat from your hands far more so than unpowdered gloves. The powder is there to allow easy removal of the gloves.
Also, dont buy the cheap ones... the Diamond-Grip gloves that Benzmac mentioned are excellent. Also check out the local suppliers that supply hospitals or clinics.
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