Awesome post Hector.
This is inspiring to try this more often. It was encouraging that if she is receptive to keep doing it as much as possible (usually someone might think if they put their hand on her butt once that was enough). I'm an ass-man (a man who really likes the ass of a sexy woman), so we might as well go for it and in a seductive way try to grab ass a lot more often.
A calibrated way to gradually start out with the butt of a new girl could be, "That's a nice skirt," and then when going to feel the fabric on the back side just happen to lightly brush your hand on her butt and notice her reaction (then if she's receptive next time such as when kissing grab her butt more).
One of the best pick-ups I've seen is when a guy was having some playful fun with a girl for a few minutes (they were doing some playful games with just their hands while standing and just goofing around), then he kissed her (he might have said something like that was fun now you get a kiss before he slowly went for the kiss), then he put his hands on her butt as he continued to kiss her, and then like making out kept kissing her and really grabbed her ass firmly with both hands and pulled her into his "front area" (and all of this was done as basically one continuous kiss in around 12 seconds).
Grabbing her ass is an advanced level way to screen for DTF. This post is a helpful reminder to put your hand(s) on her butt more often. Thanks.