AHi! I am sure there's a thread on this somewhere but I'm having a hard time finding anything. I want to know how they can use all that filling in cakes and not get the bulging?? Is it all about letting it settle or maybe ganache method?

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Who knows what those people on TV are doing or what filling they are making.  Impossible to know. You can't believe what you see on tv any ol' how.

I do know that when you make a good cake you don't need an inch of filling inside the layers.

Yes.  Inquiring minds want to know.....

I have had the exact same question for the 3 years that I've been involved with hobby baking.  My personal conclusions:

1) Those bakers/cake decorators have been doing this for about 300 years.  They have muscle memory and 10's of 1,000's of hours of experience in what works and what "isn't quite right". 

2)   I've only done about 60 hobby cakes and I'm always trying something new, so I rarely do the "same thing" repeatedly.  Skill like you observe on TV only comes with REPEATED skills. 

3)  They ALWAYS have MORE THAN ENOUGH FROSTING/FILLING AVAILABLE!!!!!  This is huge.  As a hobby baker, I have consistently prepared "too little", rather than "too much".  I finally purchased a stand-up manual defrost freezer just for cake stuff!   This way, I make DOUBLE recipes of everything I think I might need, and  freeze the left-overs to use later. 

4)  Knowing "how much" is enough comes with practice, practice, practice (and a lot of bulging cakes in the meantime...)

Personally, I have tried several methods:  Using a clean, ceramic floor tile to weight the cakes, letting the cakes settle overnight, torting/filling/freezing the cakes before crumbcoating, buttercream dam, super-stiff buttercream dam, no dam, not doing anything.  Sheesh.......

Mainly, if you are going to put something heavy (fondant) on top of a filling that's gonna squish out, put a weight on it and let it settle for 2 hours.    If you are NOT putting something heavy on top of a filling that's gonna squish out (buttercream or Pastry Pride), push down with your hand and call it good enough.

http://cakecentral.com/t/745120/dam-bulge

We don't actually see how long it takes them to make it which is part of the problem. Watching a cake settle does not make for good tv but odds are the cakes are allowed to settle. I also believe the thickness of the buttercream dam plays a significant role. His dams are quite substantial, more than say what is recommended in Wilton courses.

I recently started to dam my cakes and  definitely recommend it. An inch is high for filling imo it's true on CakeBoss they seem to make very high dams but you know, a lot of people like cream esp if it's good and compliments the cake.

Forgot to add, you definitely need to let the settle, over night if possible.