I have an Belgian sour that has been in it's secondary for 18 months. With a terminal gravity of 1010 for over the last year, what is the best way to bottle condition this beer? New yeast? Blend?
If by bottle condition you mean to carbonate, I'd add some fresh yeast. Preferably a neutral ale yeast strain like WLP001. I'd recommend using just a 1/3rd to 1/2 a vial of WLP001. Add it to your bottling bucket along with your priming sugar prior to racking over from fermentor to bucket. This should ensure more than enough healthy yeast at bottling.