I buy a couple bottles. Make up a starter with the ratio of 100 grams DME for 1000 ml. Start small for this, maybe 250 or 500 ml in size. Open the bottle, sanitize the opening, pour the beer in a glass leaving a little, give it another shot of sanitizer if you wish, swirl and dump the dregs in the starter. Repeat for the second bottle.
Then step it up to 1 or 2 liters, then again to what ever yeastcalc.com says.
More time. More work, but you have the Bells house strain that way.