I've never batch primed because I've never been really sure how to do it. And worried it won't turn out ok .
I use the "Bottling, Priming and Kegging" section of the "Calculators" at the top of this page to work out the amount to use.
I then dissolve the required amount in a saucepan with a small amount of boiling water, cover the pan with tin-foil while the syrup cools down and then stir it in after syphoning the brew off into the bottling bucket or the keg.
It really is much easier than carbonating the individual bottles. :thumb: