I found these applicators at Bunnings and thought I would give it a try, they work extremely well with the KBS..
They are just a polystyrene thingy with very soft small bristles, you can cut them with a stanley knife if needed but recommend giving it a try..
Test it on a scrap piece of ply first and you will see what I mean.. very cheap and disposable.  Much better than a foam brush which is better than a roller..

KBS will react with the polystyrene but not immediately, meaning it will dissolve the styrene. You can apply your coat then throw it away, use a fresh applicator for each coat..

SHURE-LINE Handi Painter

As Molly Meldrum would say.. "Do yourself a Favour" 

Cheers: Brettski... :)