OK, a lot of bits and pieces about "dipping" have been mentioned kinda piece-meal, and it might cause some confusion, so here is a more lengthy explanation.
"Floor Wax" such as Future or Pledge brands
https://www.amazon.com/Johnson-Pledge-F ... +floor+waxis a clear acrylic meant to give tile floors a high gloss. It can be used on miniatures like a brush on gloss coat to highlight shiny bits of a figure that has been matte sealed, or to provide a protective coating like a regular clear coat. It does nothing for shading.
Wood Stains, such as Minwax brand
https://www.amazon.com/Minwax-70012-Fin ... _i=desktopis an oil based stain that can be applied to a miniature to provide some quick shading. I have seen it used both before a figure has been painted and after. As mentioned, it should be thinned first (with turpentine?) before being used on miniatures, but it doesn't have to be. the stain will flow into recesses and provide a natural dark area that shades a figure automatically.
It takes a loooong time to dry completely (days). It will also darken a miniature a lot if applied afterward, so paint in bright colors.
Army Painter, as mentioned, creates a line of similar products
http://shop.thearmypainter.com/products ... tGroupId=1that are meant for miniatures. Their stuff drys a lot faster and, IMO, looks better than the wood stain, but is a lot more expensive.
apply either of these things can be done in different ways. You can "dip" the figures, which is exactly what it sounds like. Dunk the figure in the can and then shake it off real good. I have heard some people using this method that recommend attaching a rod beneath the figure and then using a power drill to shake the excess off, so you want to REALLY shake of the excess. This is INCREDIBLY messy, do it outside and far from anything important.
You can also use a big (~1" diameter) brush to just slather the stuff on. That isn't as messy, but you still want to do it in the garage or outside. You will need to clean the brush with turpentine or something afterward though.
Finally, it can also be applied with a regular miniature painting brush (that will not be usable for anything else, ever). this provides the most control and can probably be done inside, but takes longer and almost removed the whole point of using this stuff. Again, brush will need to be cleaned with something that breaks down oil based stains.
And again, emphasizing that it takes a long time for this stuff to dry. It will also give the figure a high gloss, so you might want to hit it with a matte coat later. Finally, if applied last, it creates a really hard shell that protects the figure quite well, sort of a super 'ard coat.