I think it's easy to get too wrapped up with this 10,000ft number. You will need to do 28,000ft on the day.
I reckon a better approach is to do a few long days out, recceing the route and work out what the weakest part of your game is and tailor your training to suit.
A quick comparison of your split times from summit to summit with those generated by the calculator on Bob Wightman's web site will give you a gauge as to where you need to do the most work.
I found I could get up the ascents in fast times at an easy recce pace, but was struggling to keep to 24hr schedule across the roughest terrain. The descents were also battering my quads. So I tailored my training to suit this by spending a year doing as much racing on Lakes classic type races (to try and up my speed over the rough stuff) as I could with long days out in North Wales where the terrain is altogether rougher and tougher than the BG route.
The Kinder dozen route and variations of it became a fairly regular training route as the up & down nature of it really knocked my quads into shape.
I averaged around 6,000ft per week in the 6 months leading up to my successful attempt, and this started lower than that but finished higher.
On both my attempts my weakest leg by far was leg 2 (Helvellyn & the Dodds etc.) as I found my body just doesn't want to work between midnight and 5 a.m. I never did resolve that one.
It's horses for courses.