Lets see if I understand this.
Step #1 Do a test print with the #389 green filter.
Step #2 pick the time on the print that looks best
Step #3 expose the whole print to the time from step #2
Step #4 Now use the #68 filter
Step #5 Pick the best time and use that to make up the print.
Am I right? I'm ignoring anything like the need to dodge/burn. Lets assume my negative is magically perfect-)).