I always bottle from the plastic conical, for BBL aged beers I CO2 purge the FV, push the beer from the BBL to the FV with CO2, add the priming, stir well and then purge as best I can the headspace in the FV. I usually prime with spiese, and regardless of whether I'm adding yeast or relying on still active yeast in the beer, I mix either the spiese or sugar with ~ 2 qts of the beer in a starter jug with an airlock to make sure all systems are go before bottling. More often than not I do this the evening before bottling day as it normally takes until the next morning before definite signs of fermentation are evident, but that of course can vary from beer to beer.