He should have applied a lot of Vaseline on and inside her asshole first, and then stuck the thermometer in MUCH deeper and spun it around inside her while waiting a long time for temperature reading, then stuck it back in again to verify the reading.
A good idea to make her explicitly explain all of the things going on...she should have had several things inserted, and been made to comment on how each one felt, also to have had her breasts bared before (presumably) going over the man's knee, and similarly made to comment on that....
Yeah, TFP.
Xxx.