Let's face it. Because of shoes and hard surfaces our feet are way over torqued. But it is really simple to loosen feet quickly.
Simply work the edge of the heel particularly the medial or inside of the heel.
If you are a practitioner simply use thumb- walking to cover the area throughly. First rotate the foot to get a sense of the tension level. Next apply the thumb walking technique. Then test again.
When you have the foot good and loose get them up and walking to feel the difference between the two feet. If it went well they should be impressed. Repeat the procedure on the second foot. See if they match.
If you are doing self help on the tailbone area a golf ball can by quite handy. Roll the golf ball along the rim of the heel. Repeat on the opposite foot.
Some people swear by using a "super-ball" They feel the slight give can be quite effective in working the tailbone area.
I will have other tips to loosen the foot. But did you have success with this technique?