Hibs went in front through Welsh after half an hour, but Kyle Faulds equalised almost immediately - making up for the own goal he scored when the two club's reserve sides met earlier in the week.
Hibs upped the ante a bit in the second half and Welsh got them back in front before Saints' Sean Burns was sent off for dissent. Russell sealed the win late on when his effort hit both posts before the officials decided it had crossed the line.