Putty for the basic bedding and liquid for the skim coats.
The putty has a bit more shrinkage than the liquid. Using the putty for the main bedding cause it is easier to use and doesn't flow as fast. Once that sets up (I'd give it 3-4 days so that you get full shrinkage),the metal will come out of the stock pretty easily. Now come back and lightly scuff the bedding (I use red Scotchbrite) and lay a thin layer of the liquid in place. That will provide the intimate contact between bedding and metal you are after.
That is my .02 worth on that.
Bob