Question re shipping lines in WW2


I gather that British liners were requisitioned by the RN during WW2 (and WW1 of course) for troop transports etc. How did that work, personnel-wise?

Did officers/crew have to be in the RN Reserve or recieve RN training or did they carry on as simply CWS crew members paid by CWS or were they paid by the War Office?

Assume that most of the non-essential crew like stewards, maids, waiters etc were not taken on or assumed other roles?

Were interiors stripped down and surfaces covered do they wouldn't be damaged?