There are a lot of different opinions on in-house vs third-party pressing. From my own experience, I get my comics pressed by a third-party before sending them in. However, I figured the comics get handled by a lot of folks for signature events and pressing in-house gets done after the signing and before the grading. I factored that in as well as worried about getting it back from a third-party to make it in time for the event, so for my first (and so far only) signature event, I had it pressed in-house by CCS. The caveat of course is the delay in getting things back and the risk of a bad press.
Probably didn’t really answer your question, but just things to consider…
And as for holos, I’ve seen plenty of SS signed holo covers available online/ebay, so I don’t think it’d be an issue…