I would recommend that you get hold of a copy of "We Landed By Moonlight" by Hugh Verity who flew many of these pick up missions. It's over 40 years since I read it but the Wiki article here draws heavily on it regarding use of the Hudson. The early SD squadrons had to make do with whatever aircraft they could get their hands on.
See under 161 squadron. A Hudson happened to be available. I have one serial no for a King's Flight Hudson which may or may not have been the aircraft concerned - N7263.
Pick up operations were only a small part of SD operations but attract the most attention. The Hudson didn't have the range to get to Poland from Britain. Most operations to eastern Europe were from Med bases by 148 squadron mostly using Halifaxes and Liberators, and which never operated the Hudson.
A mission to Poland was flown by a 267 transport squadron Dakota to collect V2 parts.