As part of the River Song cosplay that I am working on, I tried out the Jerome Russell B Blonde Highlight Spray to see if it would work as part of my costume. Results - mixed.
It was pretty easy to apply, although I'd think almost impossible to do yourself since you're supposed to apply from 12-18" away. My somewhat tolerant husband helped me out with the application, but I think that was mostly so that he could make fun of the results ;) We did it outside which I think was a good move considering all of the residue we could see in the air around us during the process.
I have a lot of hair, so it took a can and a half to get full coverage. Getting the bits around the neck and hairline was tricky, so I did those myself and ended up with sparkly gold flecks all over my neck and hands. I was wearing an old shirt during the the application process, so no issue there, and some rubbing alcohol got it off my skin pretty quickly.
The chemical smell of the spray was pretty strong, even after two hours of drying. The smell ended up giving me a moderate headache, but I am sensitive to smells, so it may not be an issue for others. Although, I guess I shouldn't have been surprised since I was essentially spray painting my hair! The spray dried a little lighter than the original gold, but since my hair is a very dark brown, I'm not sure that it got my hair light enough, which is the real issue. It looked a little goofy to be honest, so...not sure that this product is going to be for me.
I wore the color for about five hours and didn't observe any noticeable flaking of the color unless I actually touched my hair. Any gold fleck residue on my clothes seemed to be from not being careful enough during the application process, or from contact of my clothes with my hair. I'm confident that it would have lasted as long as I wanted it to during a single day.
Surprisingly, the color washed out completely with a single intense shampooing. I was worried that I'd be partially blonde for work today, so that was a huge relief.
Cost was not bad, $5.79 plus tax per bottle at my local Wallgreens, or available online in various locations. I could not find it at my local Target. So as an experiment, I'd say it was well worth the modest cost to try this out.
Final analysis - At least for my dark hair, wearing a wig is likely going to look a lot better than the hair color spray.