Complex setup for a hair salon

I am trying to figure out how to get appointment+ to work for one of my clients. He has a hair salon and uses a 45 minute time base. However, when he does some work, such as a hair color, he works for 45 mins, then waits 45 mins for the color to develop, then finished the haircut off for 15 mins. What he normally does is book in another client while the color is developing so he can fit in as many clients as possible in a day.

I have managed to change the timebase to 45 mins and add all of the services but I can't figure out how I could set it up to accommodate his requirements.

If everything is 45 mins then he will end up with no time to finish clients up. If I set it to 105 mins then he will have a spare 45 mins in the middle where he could be seeing a client. Neither really works.

I thought that there must be loads of hair salons use appointments+ that must have come accross this issue before and I wondered how they dealt with it? Any help or suggestions would be appreciated!