Doing this is not a *good* idea. You have to do it in such a way as you displace the dye already on the film, and sometimes it does not work or does not work the way that you want.

Sometimes a "J" aggregate forms causing a shift to longer wavelengths and giving an unwanted spectral sensitization.

Even worse, sometimes the dye sticks to the emulsion and leaves a severe stain in the negative.

BTDT. Sorry.

PE