Have done this to two sis in law and several friends over the years...
When visiting, when we say our goodbyes, I make a point of placing my hand so I get a good feel of tit as we hug. The first time is always the same, using the back of my hand, to gauge the reaction. The either don't notice, DO notice but don't seem to care or notice and distinctly don't like...
If they don't notice or don't care, I get a bit bolder the next time, with fingers or the palm of my hand, again gauging the reaction. They make it clear how far is far enough and I don't cross that, but I have 3 friends and a sis in law who get a full palm squeeze for as long as the hug lasts, both when the come and when they leave
. It's great when they are in an especially good mood as THEY will linger in the hug LOL