I grew a beard for fun in preparation for going sly. I ended up really liking the beard, but hated the white hairs so I used Just For Men. I got really good results considering it is very quick and relatively inexpensive. If you get the details right, it can look very natural. You may have to experiment a little to match the right color. Also, careful about leaving it on longer than the prescribed time. As they say on the packaging, this will not make it last longer but rather make it darker than advertised. Maybe if you feel like you need to keep it on longer than a minute or two over the prescribed time, you actually just need a darker color?
I could get several uses out of what is inside one package and needed to do it once a week to keep the gray mostly out. I think it is a pretty decent product.