If I can tell a story,... Many years ago my shop partner had a job with matching veneer. The matched panels he bought were exactly enough for his job. His only problem was the top panel had been in the sunlight for years so the A face had a sunburn (for lack of a better way to explain it) The rest of the panels were all consistant in color. When he sprayed the job, that sunburned panel was redish compared to the others, so he asked my dad if there was anything he could do. My dad mixed him a toner with an invisible amount of green pigment in it for him to spray on that one panel to kill the warm tone that panel had. My partner sprayed two coats on the panel out of the cup gun. It looked better, but it looked like one more coat would bring it in perfectly. My dad told him not to spray the third coat, because when it flashed off the toner would be more concentrated and the color would be stronger than it appeared while the coat was still wet. My partner decided to give it that extra coat anyway after my dad left our shop. In the end, that panel that needed the toner was a just a hair off color on the cool side because of that extra pass my partner's eyes told him the panel needed when he looked at it when it was still wet.... My partner said later, "I should have listened to Arty!" and he realized that Arty had "the eye, the knowledge, and the touch" of a master.
My dad is gone 20 years now, his mastery was widely recognized in the New york area. He worked for a smaller union company as the foreman of their finishing room. When some of the big companies got in over their head on a particularly hard finish, they would hire the company he worked for so he could get them out of trouble.
Sorry for the rambling above, but my message is as I said above,...
Toner will seem more transparent when it's wet, so don't give it that extra pass because it's "almost there". When it dries it will "get there", and if you determin that it needs another pass after it's dry you can usually still do that, but you can't sand toner to even it out and you can't take back that extra pass.
Finishes like fireflake have a variable tone, so I bet the range is not as easily detectable to the naked eye. You may end up with a pretty undetectible freshen up. Good luck, I look forward to hearing it worked well.