I don't read BYO, so I can't help you with what is actually written there.
But I'm using this technique for all my lagers. The primary fermentation is done in a carboy and I will rack to the secondary/lagering keg when the remaining extract is about 2*P above the FG (generally after 7-10 days). If I plan/have to rack later I usually add Kraeusen to ensure that there will be enough yeast in suspension and extract to carbonate the beer. Then I let the pressure rise and blow off excess pressure manually. I haven't build myself a nifty pressure sensitive valve for that yet.
This is just another brewing technique that is used by virtually every German brewery and all the bigger brewers in America.
I recommend the primary fermentation in a different vessel since you want to take the beer off the yeast cake for the secondary and lagering and you cannot do a primary fermentation of more than 4-4.5 gal in a corny keg due to the needed head space.
"I have never done this, so I'm no expert, but this is how I understand it and I think it is problematic as I like to secondary my beers for a couple of weeks before priming/force carbing."
The big boys must have a way of dealing with this. Filtering ? I'm interested to know, if anyone does know.
short description of the fermentation in a taditional German lager brewery:
- primary fermentation in a conical fermenter at 8-10*C for about 7 days. During the end of the primary fermentation the beer is slowly chilled to about 3-5*C
- racking to the lagering vessel. This happens with a remaining fermentable extract of 1-2 %. This vessel is spundet, meaning pressure can build up to achieve a CO2 content slightly above the one that is finally needed.
- optional dyacetyl rest at 3-5*C
- lowering of the temp to 0*C for lagering
- then they may add PVPP (polyclar) and filter using plate or diatomaceous earth filters
- adjustment of the CO2 content of the beer depending on the CO2 content needed for bottle or keg.
Once the beer is racked to lagering everything happens under pressure so the CO2 can't escape. This is economical (no extra CO2 needed) and necessary for Reingheisgebot compliance (only fermentation CO2 can be added to the beer).
I try to mimic this process as much as it is reasonable for a home brewer. My process differs only in the fact that I rack at about 10*C and let is rest there for a few days before getting it down to lager temps. I'm not sure if this makes a difference though.