I agree with Kathy, I wouldn't give him dairy right now...
I'm gonna try to put our advice into perspective, explain a bit about why we're making the suggestions we are...
It's been at least a couple days since he has eaten, he needs more than a slurry can provide especially being injured... tube feeding a balanced diet will go a long way to helping him recover quicker and less traumatic than him trying to eat with that injury... yes, animals compartmentalize pain better than we do, but any pain you can avoid the better...
Tube feeding is not hard, the mental part of it is the hardest... Kathy made a great thread on it and is willing to answer questions as well...
Also, since the core of the upper beak is exposed, you definitely want to avoid not only contamination that can cause infection, but also damage... the keratin can grow back over it, but if it becomes too damaged or it breaks off, then that part is gone... any way you can encourage better odds of his beak healing as close to what it was, the better... especially considering the drilling he likes to do...
Talk to your vet friend, if she can't refer you to a bird vet, she will at least know general supportive care for injuries/trauma and may even have additional ideas... couldn't hurt to ask at least...
I hope this helps and he heals up well...