The whole act of making the albumen mixture is the best part of the process. I admit I never tried the pre-packaged egg whites, but you'd want to froth them up anyway, so there'd be no big time savings. You'd still have to let them sit overnight, but I'd imagine whipping them would get rid of most of the impurities. Guar gum. What is that crap anyway?
jdef, start with 4x5 if you've never done albumen before. You'd be surprised how much more difficult it is to get an even coating on larger papers, which is why I've only done albumen in 5x7. I'd agree with hermit, though, that Strathmore 500 is a great way to start. I still tend to use Cranes Kid Finish as an all-around paper, though it's light (32#) and tough to handle sometimes; it curls like mad with albumen.
Here's the tip of a lifetime for albumen: when you're coating and the paper tends to curl up and away from the solution, breath on the back of the paper to get it to relax. I used to use a light mister kind of spray bottle, but a friend of mine turned me on to the "hot breath method". Haven't looked back.