:Mornin,
you should be able to avg. 6' per hour on 4 6 and 8 plaits. core makes no time difference. 12 or more will take u to bout 4' per hr. a pineapple tied and finished should take about 10, 15 min depends on the width of the string.
as far as getting faster. the best way it practice. good needles help a bunch. a scary sharp knife is a must. a pair of mosquito hemostats help. But the thing i think you need to hear the most. is . Braiding is prep work. the better you prep the better your work. the more u prep the better your work. Prep a hide for a string. prep a string for a knot. prep knot for an interweave. prep a knot for a finish. It only takes 15 min to tie the knot but u have an hr or more total in the 3' of string u are using. the better you spend that hour and the more prep you get done in that hr. the happier you will be after that 15 min. Where time is really made up is n the string cutting. My set up will take a whole hide ( tempered ) and strip it out to 1/2" and stretch it up in about 2 hrs. the next day ill spend another 3 to 4 hrs splitting, re gauging and beveling them. so that is only 5 hrs. for over a 1k' of string. most braiders i have met cant touch those cut times although some are faster braiders than i. so spend just as much time thinking about mechanical advantages as u do over two under two. some body with a cord less drill is gunna get a hole drill faster that some one with an old had crank Yankee.