Hi Dyehard!! To be honest, the first advice i would give you is to wait as long as possible before doing anything more to your hair. I completely understand not wanting to show up at your son's school looking like a hairdresser worked on you for an hour then fell asleep for 5 before finishing the job! I have had that problem many times over the years. I believe that using a NON-PEROXIDE SEMI PERMANENT hair dye is the way to go. But i always recommend washing your hair the day before colouring again, to make sure every single trace of B4 is gone. It's best to wash once, using an intense conditioner, towel drying alot then repeating the whole process. The best methods to get your hair how you want it, in my experience is to buy some of the little colour sachets that shops sell. The ones that wash out after 3/4 washes. If your hair is left with red tones, buy sachets with ASH in the colour (ash blonde, ash light brown). If you have long or thick hair it's best to use 3 one after the other. In other circumstances i always suggest people use 2 to help tone down any red. It's usually best, to then wait until the following day to dye the hair. If the ends are reddish, before using the semi dye, make the lengths of the hair wet ( but towel dry lightly) then apply the dye, otherwise the roots are likely to be lighter. But really, the best bet, if you have the time & money, is to do the sachets for 2/3 days before dying. You can use 4/5 sachets if you feel the need, depending on how reddish or darker you feel your hair is. If you choose to do this process i STRONGLY recommend doing a strand test with the dye to give an indication if it's going to work. I went from a year of mahogany brown, to light ash brown. I had lots of build up and had to do all of the above. It worked for me & i'm glad i wet the ends of my hair before applying the dye! My hair is long but not thick. It's good that you have the school hols to fix things, so just go at your own pace and see what the sachets do for you first, then go from there. I hope this helps. Also, if you are looking to go blondish, best to go light ash brown first, then after 2/3 weeks, you can work up to the desired colour. Good Luck!! Let me know how things go!!