I was in Magic Kingdom last week and used
Genie+ there twice. I do not find the stacking strategy to be as useful at that park as it is in Hollywood Studios. I used the "Use and get a new one" strategy and had a lot of success with it.
On our first day there I got Jungle Cruise at 7am for a 9:30am - 10:30am window. We got to the park at 9am and went on Pirates (had planned on heading straight to Thunder Mountain but it was down) with no wait as soon as they opened Frontier Land. Then we went on the Magic Carpets quickly just to kill 5 more minutes before our Jungle Cruise window opened.
As soon as we tapped into Jungle Cruise, we got another LL for Haunted Mansion for 10:30 - 11:30. While we waited for that window to open we went on Small World which only had a 15 minute wait.
After tapping into Haunted Mansion, we got another one for Winnie the Pooh good for 12:30 - 1:30. Ate lunch while we waited for that window to open.
We followed this process all day long, basically using our LL's on things with more than 30 minute waits and filling in the rest of the time with things with minimal waits.
Almost all of the Hollywood Studios attractions LL return times move several hours into the future making it a good park for stacking. This is not the case at Magic Kingdom where the return times stay fairly close to the booking time. Magic Kingdom also has a lot of attractions with low waits that you can fill the time with while you are waiting for your
lightning lane. Also not the case at Hollywood Studios where most of the attractions have long standby waits.