Malto-dextrin adds no flavor to a beer. It is strictly used for body and head retention. Also, two ounces of lactose isn't too bad. It should help out nicely.
As for what to look for... Malto-dextrin can be found in several forms. I first used it as a white powder. It looks like lactose, priming sugar, etc. The second form is as a malt. It may be labeled as Carapils, Dextrin Malt, ...



