Hi Ken Fu,
the simplest and easiest way in my honest opinion, is shield and earth everthing.
I only use conductive paint in the bridge post holes, I use shielded push back wire, like that sold by Stew MAc, but it is freely available on ebay. I use copper shielding in all cavities. I do not, repeat do not subscribe to the idea of earthing the pots to the shielding. AFAIAC that concept is a bit too hit and miss, as it requires you to make sure the pots contact the shieldong as some may suggest, or you have to solder a tag to the shielding. I think you get a better result from using shielded wire.
As for split coils Love th idea and have done it a few times. You can dismantle two wire coils and do your own split, but beware you may end up with a couple of paper weights. Yep been there done that.
You should have a look at Seymour Duncan tripple shot pick up rings. these make the whole wiring in split pick ups easy.
getting the wiring right for split coils using push pull pots is a whole lot of fun and guaranteed to end with a few burn spots on you fingers. But it is worth the effort.

Cheers PK