I saw this line 3 weeks ago, but decided to leave it to ration what little supplies I have as long as possible. An advantage of travelling is that I rarely saw myself in a mirror while I was away!
I couldn't ignore the roots any longer so yesterday I mixed some (no all) leftovers I had from last year in a mug and applied it with a cocktail swizzle stick, turns out you don't really need gloves or the bottle with a nozzle.
It wasn't a 100% success, either because I didn't use enough or because the tubes of colour had been open for months, but I think that is probably for the best since I will be leaving it too long again before my next application, so having uneven coverage will mean that the line between the dyed hair and roots shouldn't be so obvious!