Try to pick up a few Vietnamese phrases like “Em khỏe không? (How are you sweetheart?)” or “Em thật dễ thương ( you are very cute or beautiful) and so on. If you can speak some simple phrases and offer 300k or 500k tip for herself then you may get FS. Remember the key is to not let the mommy know about it. Just go in as normal then negotiate with her so she does not have to share the tip and you do not have to pay more to the house other the than the usual fee.
If you can venture out to Gò Vấp or Bình Thạnh district you can find more local KTV and HTGD at cheaper price. Even SW are available on Tân Sơn street in Gò Vấp district or on Nguyễn Chí Thanh and Đào Duy Từ street.
I found that NPK was a way better value and deal that Tiffany Spa in D7 that you suggested. There are a bunch of NPK hot tocs, and you will eventually find a hottie that suits your taste, and you get the guaranteed BBBJTCIM.
At Tiffany Spa, there were like at most 4 masseuses working, all fobby and below 7's, and some don't prefer to CIM, just BBBJ.
The price tag at NPK is 400K VNd (i usually just give them a 500K note for a great service IMHO) and at Tiffany Spa it's 800K VNd. Plus, NPKs are closer, whereas Tiffany Spa is out of the way and takes 20 minutes to get to and 20 minutes to get back home.
If anything, i think Tiffany's is overrated until they get some prettier girls.