My racks are long out of production AV123 short 3 shelf units that are very rigid and I glued Herbie's Giant Fat Gliders on each leg. Each component is isolated by some form of Herbie's product. Most are Tenderfeet, Fat Dots, or Baby Booties. Although I have not used an accelerometer to measure the effectiveness of the devices, my ears do detect better clarity in the system. I make sure the mechanical units (spinners, turntables, valve gear, etc) get the better ones and components with no moving parts (SS gear, DACs, tuners, etc) get less attention.
That's my general approach. I think vibration isolation is dealt with in two disciplines of thought, mass and rigidity, or suspension and flexibilty. To couple or to uncouple, that is the question. Of course any combination of these two schools can produce better results.