The part about going thru the US Atty and a grand jury is the modern, dumb, lazy, way to do it. Used to be a purely Article I process just as judicial contempt just needs the judge to act.
Congress can imprison Wray and Rosenstien for contempt, and use some room within the building for that purpose. They can then take away his cell phone or monitor all his phone calls that are not with his attorney, which he would have to pay for.