the lock shields wont be a problem the trvs can be if the close completely to a O then your okay if they only go as far as a ‘snowflake’ they will leak sooooo whip the head oof and put a penny under the head and screw it back together the penny will apply enough pressure at ‘snowflake ‘ to fully close the system..
drain it off as per the pic above you ll get anything up to a washing up bowl full any more and one or more valves aint closed..
the initial water may be nice and clear at the end when you lifty it off any remianing water will be black like oil and harder tyo get off the carpet etc so be prepared lots of loo roll to ram in the open ends..turn the rad upside down so no chanc eof anything dripping out..
one tip when draining the rad open the air vent on the rad to release any vacumm..
ps i ve heard there are blokes called plumbers who can do work like this..