There is usually more than one answer to the Bingo problem...
In the 744 I routinely set my Reserve Fuel in the FMS to the minimum of Flight Plan FMS Reserve or [7T + burn to Alternate]. That is my target minimum fuel at the threshold of the primary destination.
When in holding, I can then input EFC times in the HOLD page to get an estimate of my latest departure from hold before I will have to divert and/or call minimum fuel. I can also set up a whatif in ROUTE 2 for a divert route from the current holding fix.
Without the magic, I figure on 10T/hour average, and estimate my time to alternate considering winds. Get there with 7T minimum.
I'm sure there are other techniques...