There is a bit of plastic inside the boot lid that pops out, some screws behind there and take off rubber stoppers the other end and some torx screws behind there too. For the other half the light in the rear quarter undo 2 torx screws and they are then held in by a metal clip, give them a thump pushing them outwards, the first time they are hard to remove.
I tried tinting my rear lights and it looked crap, but was not proper tinting spray, looked good an my mates Focus but cos the FR lights are so light behind it shows up the spray marks. Go for tinting film easier to remove if looks crap as well!