Thesnow, here is a reply I made a few days ago on blending Zinfandel. Might give you some ideas.
"DCJRW, earlier this year I attended a short seminar conducted by Jan and Tom Cobett at the Pittsburgh Amateur Winemaking Competition sponsored by the AWS. The title of the seminar was "Blending in the Zinfandel Patch" and it involved blending wines to our particular taste using Zinfandel as a base and adding varying amounts of Carignane, Petite Sirah and Grenache. Each of the three "background" wines added something to the Zinfandel (Carignane added acidity, tannins and color; Petite Sirah added color, texture/mouth and bouquet; Grenache added body and fruitiness) and we tried several combinations. The combination that I made that I personally liked best was 60% Zinfandel, 15% Carignane, 10% Petite Sirah and 15% Grenache.
Now in order to blend 4 wines at home would require a fairly large operation. An approximation of what one would get from various blends could be attained by buying bottles of commercial wine and trying the combinations first. The issue with this approach is that, depending on the wine one buys, a Zinfandel, for example may only be 75% Zinfandel and 25% unknown varieties unless they are listed on the label. Some wines list accurate percentages of the varieties included, some do not.
In any case, it was an informative seminar and went somewhat into why various wines are blended with others."