Ok...the baby may clear all the stuff out of the sinuses by morning. Some though may irrate the eyes, and also leak out or bubble from the corners of the eyes as he is trying to clear it from inside. If he sounds fine by the AM then there may be no need for a flush, but the vet might put him on oral antibiotics.A lot of gurgling is coming from his nose/head. I'd say, most of it. Okay, yeah. How does a vet do a sinus flush? Is it possible to help him in any way, and is it possible for them to get it out themselves?
I would ask the vet for a dosage to be mixed in his formula. You can have him calculate it for the amount fed per feeding. OR if he wants it given separate from the formula, ask to be shown how to gavage or tube feed it. I'm a chicken when it comes to orally medicating a bird, and always crop tube medicate.