A mini tutorial could I say. More like..I am more using to color than gray scale BUT i felt 'ok time to do gray scale'
many like me can have it hard sometime. Some use overlay and so...but try color layer. Just careful with the colors since more lighter you use it gets...yeah, not the color you want.
so I used color layer over the gray scale, then i added multiply (under color) and very low down to 15 - 20 opacity.
I add another color layer to add on the suckers (lol I said it...hehe)
Then i use the last touch to use color dodge (which give like glowing) very careful where I was to add color
then I add color balance to find the right one..then last the hue to make sure it do not get too dark either.
Try it out ^^ it's fun!