We did this last week for our second DHS day. Slow morning (after booking 7AM SDD LL), pool time, went to DS for lunch then to DHS.
Arrived at 2:30 and did a ride we didn't have a LL for. At 3:00 we hadn't used any of our LL's and had the following stacked:
3:35 - 4:35 Star Tours (booked at 1:00)
3:45 - 4:45 Toy Story Mania (booked at 11:00)
3:55 - 4:55 Slinky Dog Dash (booked at 7:00)
6:00 - 7:00 Tower of Terror (booked at 3:00)
The thing that worked well for us the few days I purchased Genie+ was to set an alarm for 5 mins before we were eligible to book the next LL. That way we weren't spending all our time clock watching. Also, in the 5 min window we would look at return times to determine what we were going to try to book when our window opened. We could have booked more LL after 5:00 but there wasn't anything available we wanted to book.
It was a bit of a learning curve but for the crowd levels we experienced last week, Genie+ worked well for MK and DHS. We did not purchase for the other parks or purchase any ILL$. The only 2 ILL$ we wanted we rode at rope drop (Remy) or park close (RotR and SDMT).