I've never used that product, so I can't comment on it, but you might like to try some other ways of doing a wash.
You can take flat black paint and thin it down about 50:50 and use that as a wash. I thin down good old Testors (the little square glass bottle) and flow it on. Sometimes a quick wipe with a paper towel (or my finger) to bring out the raised areas, and you're good to go.
You can also try thinned down black ink as a wash, as well as acrylic black paint. If you mess up, water will take care of your mistake and you can try again.
There is also a spray by Testors called "Transparent black window tint" that I've used with good results. It gives chrome a sort of bluish-black look that I like...it tends to tone down the too-bright "model" looking chrome of kit parts, IMO. I especially like it on motorcycle engine parts and chrome spoked wheels. It gives the chrome parts a nice "depth".
There are many different products you can use to get good results. Personally I like to use stuff I already have on hand anyway, rather than buying a specific "wash" product...but that's just me, the "frugal modeler"...