Well it depends on what kinda
plant it is. If you just wana get the soil moist enough so that its holding water pretty well, then whatcha wana do is gently mist it, or use a sink spraygun to gently water it so that water goes all the way through the soil, and eventually drips out the bottom. This should take a little bit of time.
But you should figure out what
plant it is first before you water it like that. Some
plants like to just have water quickly dumped in so it just goes past the roots n stuff.
~Phoebe