From the New York Times article on this currently:
Any arrest and processing of Mr. Trump would probably combine the routine steps that every defendant experiences — fingerprinting, photographing — with the pomp accorded to a former president,
whose every move is attended by the U.S. Secret Service.
It is unclear what kinds of accommodations Mr. Trump would receive. It is standard for defendants arrested on felony charges to be handcuffed, but an exception could be made. As he awaits his court appearance, it is possible that for security reasons, he will be detained in an interview room or another confined area, rather than in a holding cell. And after Mr. Trump is arraigned, he will almost certainly be released without spending any time behind bars, because the indictment is likely to contain only nonviolent felony charges.
Early Saturday morning, there was little evidence that Mr. Trump’s new demand for protests had been embraced by extremist groups.
His indictment by a Manhattan grand jury is expected, but its timing is unclear.
www.nytimes.com
So, here's a very interesting question: Since former presidents have AFAIK a permanent Secret Service detail, what happens if Trump is sentenced to a significant time behind bars (not for this, I presume, but for some other offense, e.g. the wanton disregard for the nation's secret documents, purloining and hiding them), e.g. 5 years (I would love that to happen). Does that mean there will be a Secret Service detail with him at all times in prison? I suppose that wouldn't be exactly like them being incarcerated. They might eat better than him, and I imagine they'd be switched out with alternates regularly... maybe different SS guys for each day of the week. Hardy har...