https://developer.valvesoftware.com/wiki/Cubemap

You should have at about one in every room or locations with lots of contrast (an all-white room next to an all-black room). You might want to place one next to each reflective surface in your map (glass, certain metal models like funnel emitters).

Did you rename the map? If you rename a bsp file the cubemaps will become invalid, creating that on any reflective surfaces. You should have run 'build_cubemaps' (with the map saved in portal2_dlc2/maps to avoid a bug) to generate them correctly.

It's probably more that Valve didn't bother making special gib models for them, especially since they only ever actually explode once.

Alternately you could just put them all in one instance with a turret and reuse that. To do the 'knocked over' lines, put a small trigger around the top of the turret. OnEndTouch the turret has fallen over and you can play some lines. If the turret is picked up Kill the trigger before it activates those lines (since they wouldn't match).

There's a bug with Hammer that stops you hearing any of the voice lines, but they still work ingame. The Portal Wiki has a list of all the Defective Turret[theportalwiki.com] voice lines, which you can match with the VCDs. (The linked URL has the same filename as ingame).

Make a logic_case with a bunch of different outputs, then trigger the PickRandom input to play a random one. (If you use PickRandomShuffle, it'll only repeat a line after exhusting all the current lines.) If you have a lot of turrets, you might want to set the ambient_generics to Play Everywhere and then reuse them for every turret. Give the logic_cases names starting with '@', and you could put the customised turret in an instance to duplicate it easily. For the turret you might need to set the 'Load defective models' option if you get a 'model not precached' error on map startup.

Set the type to skeleton and it'll still work correctly. It still plays the regular voice though, so you'll need to set the "Gagged" option and manually trigger lines with a logic_choreographed_scene / ambient_generic. Turrets have their OnRetire/OnActive outputs which you could use.

Sicklebrick made a pretty good tutorial[forums.thinkingwithportals.com].

Get a copy of Propper[tophattwaffle.com] working. It's exactly for this, it lets you compile a VMF into a model with all the correct textures using a modified VBSP. It's not updated for Portal 2, so your best bet is to get an older version of the Source Engine (I use 2007) and install in that. I then extracted Portal 2's VPK into the "sourcemod" 's folder so it can use the textures.

I compiled the models for you as well[www.dropbox.com].

I highly suggest using env_beams, they work much better. There's a keyvalue to control if they can be blocked, but I'm not sure what affects it. Redirection cubes would only work on Discouragment Beams (unless you build something yourself), but that's probably a good thing.

So, I'm TeamSpen210, and the author of the BEE2 addons pack. Recently I've been involved in rewriting the BEE2 itself. Because of this, I don't really get much time to map, but hopefully I'll be able to play and vote on some maps. I have made a couple Hammer maps, and I suppose by proxy my work's been in many, many maps (some good, others bad).