The problem with cleaning a complex fine tolerance machine with compressed air is that the top layer of dust on the oil just gets driven in, making the oil gunkier and more likely to bind instead of lubricating. I run into this problem a fair amount, since I too use old tools as long as they still work, and I have a large powerful compressor (currently dead, but I ordered the new piston this morning).
If the shop is even minimally competent, I doubt you'll regret having it professionally cleaned while you still can. Tell them to give it their top-of-the-line full treatment, no shortcuts! Maybe they'll sink the core into an ultrasonic oil bath, or something equally extreme.