The LED strips I used were
the ones from Comet. They have the 3M tape on the back which seems to do a pretty good job holding things in place.
For the two rear blue ones, I attached them to the back of the chrome metal ball guide thingy. I don't know what that thing is called. I stuck them high up on the metal so the most light would hit the plastics. The strips come with #44 bulb adapters so I just used the existing bulb sockets. No extra wiring.
The one under the pop bumper was a touch more tricky to get into place. This machine uses the pop bumper type where the whole pop bumper goes through a large hole in the playfield. At first I stuck a LED strip around the front edge of the hole but found I couldn't weasel the pop bumper past it. I had to put the pop bumper though the hole and then put the strip in place. Not a lot of room to work with, but I got it. I fed the wires for the LED strip through one of the holes for the pop bumper light. As it turned out, there is a GI junction under the playfield right next to the pop bumper. I soldered in on there.
The only extra light I might add is under the plastic by the upper flipper. There isn't a light there. I think because the upper flipper assembly is occupying that space under the playfield and Stern couldn't do the standard "drill a hole for GI bulbs" in that area.
I'll make a metal or plastic bracket for another LED strip. It would point the light at a 45 degree angle facing to the rear of the playfield. This will light the underside of the plastic and the upper flipper area but won't shine in the players eyes. There is a GI bulb just under the target so I can tap into that and run the wire up through the hole for the target. Should be pretty easy.