Yes, Vaniqa (spelled without a "u") does work and yes, you can most certainly use it while you're shaving (well, not at the same instant, of course!). But it's very expensive and all it does is (eventually) slow down the regrowth rate a little bit as long as you keep on using it for ever.

The only situation in which I can really see it being useful is if you've got to shave more than once a day -- it could be a help then, but I've always found it quite easy, if necessary, to keep my rechargeable Norelco (men's) shaver in my purse -- it's quiet enough to use in a washroom and only takes a few seconds.

Vaniqa is a lot of money for very little gain, unless your facial hair growth is very light anyway.