Purple index fingers. that’s one thing the ‘Rabs got right. Make ‘ém dunk after voting and arrest anyone trying to vote with a dirty finger.
Unfortunately, early voting can frustrate the finger-dipped-in-ink system by allowing days or even weeks between different votes, during which time the ink can wear off and/or be washed off. IIRC, VA has early voting in federal elections.
One other factor concerning this issue: The 'Rats now own the VA AG's office, having stolen it via a recount or two last November. It would be extremely unlikely that anyone engaged in multiple voting would be prosecuted, because most 'rats think that this practice is non-existent, and clamping down on it would be "suppressing the vote."