Like many web sites that push a product but also give good advice that will really fix the problem (cf diet product sites that in small print or instruction state you need to exercise 30 minutes a day in addition to taking their product), the web site you linked to does spell out what you really need to be doing

[quote]3. Stretch the muscle. Slowly open and close your jaw continuously
[/quote]

The website author's "trismus" resolves itself on its own by his own admission the next day, but since he claims that Tums(step #2 right before stretching) will resolve Trismus [quote]in less than an hour!!!! (emphasis in the original)[/quote], what have you got to lose.
Take one, wait an hour and post back here.
Charm