Plan on one to two weeks. New arrivals at FCI McDowell who are destined for the camp typically go through a quarantine period in the SHU first before being released over to the camp side. This is standard intake protocol at that facility and is not a disciplinary placement. It is a holding and screening period.
There is not much you can do to speed it up. The quarantine process runs on the facility's timeline and is handled by medical and intake staff. Being cooperative, compliant, and easy to process is the best position to be in, but even the smoothest intakes still take the full week or two. Trying to push or negotiate it shorter typically does not work and can create friction you do not want at the start of your time there.
The SHU portion during intake is temporary and worth keeping in perspective. Once you clear quarantine and walk over to the camp, the environment opens up significantly. Camp is a meaningful step down in restriction from the main facility, and the routine there is considerably more relaxed than what the intake period suggests.
Send mail to the facility right away so that letters are waiting for you when you arrive in the camp.