The big-big technique is the one to use but you don't run the chain through the rear derailleur. Wrap the chain around the largest cog and the big chainring, overlap the ends and add 1" (2 half-links) then cut the chain at that point. If you need to adjust a half link to get the ends to match properly, go a half-link longer. Then install the chain through both derailleurs and join the ends with the special pin or master link.

Once the chain is properly set for big-big, the addition of a granny ring of whatever size you use is immaterial. If your rear derailleur can't wrap up all of the needed chain for small-small, just avoid the gears it won't handle. Going to a too small-small combination is just a nuisance. Using big-big, if the chain is too short can (read will) be a mechanical disaster.