Great video, VERY pertinent to the horde of new mappers we have lately since the biggest issue I see with most new maps is scaling.
I always have a visgroup in my maps that I call "scaleRef." In it, I have player models and sentry gun models (as prop_static so even if I forget to hide the visgroup, they don't get compiled). Usually I go with sniper, heavy, and/or pyro. Sniper models are great for checking sniper deck visibility. Creating this visgroup is the first thing I do after making the first brush.
For sentries, I set the fade distance to 1024/1024. Then whenever I select the sentry model, I can see the coverage that a sentry in that spot will have in a nice little bubble.
Glad you mentioned the VDC wiki in that vid. Sometimes I will set fade distances on a scout.mdl to his jump height (320 hu) to make sure scouts are able to access places I want them to be able to go. You can also do this for movement speed if you like, but I find it better to compile and actually time how long it takes for each class.
Finally, this vid is actually worth a watch. It was made for CSGO mapping, but making your first layout like this -- eg, no walls, just floors and timing how long it takes each class to get to points of interest -- is a really good way of getting scaling right. It's useful to modify it for TF2 by add planned height variation to the floor sections.
http://www.worldofleveldesign.com/c...-top-down-layout-to-bsp-block-in-workflow.php