I just load up a thin brush and apply by hand! I do believe a store out there does have syringes of XHT-BDZ, but I've not found the need to order them.

Built two QK65s and I find the included OwlStabs to be quite comparable to Durock V2s. The most notable difference I've found is that the rear gap on the stem is quite small, so "plugging the butt" can be a bit more difficult/messy.
They include small wire "rests" which are a novel idea, but do mind that too much padding (included PE foam layer, etc) WITH the wire rest can add too much upward pressure and friction to the wire, which slows down the key.

Started turning to Krytox XHT-BDZ for stab wires because of this.
Holee mod was a bit too finicky for me, so I just "plug the butt" with XHT-BDZ. It caaan dry out and settle, but it being thicker than 205g0 helps tons.