Waz...I put some glad wrap over the neck of the spout and do the red cap up tight after each guitar. Whilst it is in use I just do up the red cap.
My one litre can is over 1 year old and has done four jobs and is fine.
Even with pretty OCD masking I got some bleed through and my stains mixed in a couple of places....blue and yellow....make green.
But on the necks and the body the poly...which does have a honey tone....has not made my blue colour too green at all. I would still recommend it over Tru Oil to not make a green colour....oh sanding sealer before the finish makes a difference too.