how to mash RED potatoes and keep them fluffy?
Red potatoes are my only choice for mashed potatoes. They have a creamy texture rather than fluffy, so you need to know that. You will not get the same texture as you would with russets, but for my taste, that's a good thing.
Here's what I do. Bring butter and your choice of liquid - I usually use half and half, although I've used regular milk as well as heavy cream at times - to room temperature. I never measure out an exact amount, but I would estimate that I use one to one and a half tablespoons of butter to a pound of potatoes, and a generous splash of milk/cream, probably about 1/8 to 1/4 cup (these are rough estimates). After boiling, drain the potatoes but keep them in the hot pot with the lid on. Add the butter and liquid to the pot, add salt & pepper to your taste, and put the lid back on for a minute or two. Mash right in the pot with a potato masher - not the kind that looks like a bunch of S curves, but the kind that is a circle of metal with holes in it. Mash vigorously just until most of the lumps are gone, scraping the sides etc. as you work the masher around the pot. Don't over-mash, don't use electric beaters. Both will make gummy potatoes. Taste the potatoes. If they seem a little dry, add some more liquid, a little at a time. Taste the creamy goodness!!
iluvcookies' suggestion of a potato ricer is also a good one. I've used one with great success, but unless it's a large one, it can be slow-going and the potatoes have a tendency to cool off unless you keep them covered before and after you rice them, and you work quickly. But a ricer does give a fluffier result. Just stir in the butter/cream/S&P after the potatoes have been put through the ricer.
I hope this helps!
Only way I can think of is use a ricer. GoodGrips has a nice big one that BB&B almost certainly has in stock, if you don't have one already. Ricing the potatoes avoids the starchiness/glueyness that mashing (or worse, whipping) will develop. Now, if your family is expecting red potato SKIN in there too, I can't see any way to get them fluffy; "smashed" is how I do that kind of potato when I want the skin to be in the final product. This involves lots of butter, but no cream or milk, and gently breaking them down them with a masher (the heavy loopy wire kind) instead of pulverizing them into a smooth mass. I hate potato glue on the table, as I suspect you do as well, which is why I've converted almost completely to the ricer method.