Touching her subtly?

I'm reading Art of Approach and am just curious when you approach and your talking to someone how do you touch subtly?

subtly means very light and unnoticeable , well you have to gesture and touch them on the arms of shoulders while your making your points,or you can use your touch as a reward, like hug her if she gives you an ioi

I know what it means but how do you touch subtly? Like ok I'm into my sisters friend and she's over staying over one night. So i'm talking to her what would be good subtle touches

just touch her while making conversation it could be anything , for example you wanna get up and get something from the kitchen you say "Im gonna get something to eat(touch her on the shoulder) do you want anything?) or she tells you shes in to basketball you might say something like "basketball players are cool, high five"
if she looks upset you can say" looks like you lost a best friend, need a hug?" make sure when you offer a hug you put your hand outwards so she is less likely to refuse, remember the touches should be placed for no more then 2 seconds and dont look at the location your touching, it makes it feel unnatural

So say her and my sister are talking in the kitchen I walk past her "hey Blahblah your back again" i say with mock shock like "wow your still hanging with my sister" as i walk by her my hand touches her back.

Wow 2 seconds, its amazing that two seconds can start the process of breaking touch barriers and getting her interested. Thanks