How can I make a silky smooth, rich mash? What are the key factors in making silky smooth (non gluey) mashed potatoes. 

What technique has the best results?
Here is how we made pomme puree at the restaurant I used to work at, for a very well known (in Canada anyway) French chef:

Peel and boil as many potatoes as you need. Cook until slightly underdone.

Run the potatoes through a ricer/food mill. Then--this is key--scrape the result through a tami--a very fine mesh sieve. Most often used for sifting flour. Usually about 14-18" diameter, looks like a drum.

Return resulting potato to a pot, add melted butter, cream, salt, pepper, nutmeg to your desired consistency, stirring all the time.

If not serving immediately, chill as fast as possible, and reheat to order in a pan using a little more cream to loosen it up.

IMPORTANT: you must work as fast as possible; the potatoes need to stay hot the whole time or will become gluey.