no. the -res only works for the holder. not only that, -res works at lower effectiveness for immune monsters (-res is different from both conviction and lower resist). best (cheap) bet would be to shop a wand with lower resists charges and carry it on switch.
other options for LI are: demon limb enchant charges + jab or tiamats rebuke + demon's arch while using jab. if your merc is good, he can also take em down too.