CyndeeCyanide
Posts: 95
Location: Milwaukee.
Current Hair: Pastel and Neon Pink.
You could try mixing in some relatively thin conditioner. Rubine is pretty dark, so you should be able to do this without changing the colour too much. Just make sure to only use as much as you need to thin out the dye a bit; for instance, if the colour of the dye is visibly changing, you've obviously diluted it too much.
Also, how are you applying the dye? (i.e. Do you have a system, or is it just sort of haphazard? Do you have a tint brush, or do you just use gloved hands?) This can also effect how easy it is to apply. In my expirience, applying dye at the part with a tint brush, then parting out a thin piece, apply the dye at that part, and so on and so forth until all the roots are done, then applying to the length in sections is the fastest and easiest way to do it. And in my expirience with thick hair, a cheap, wide toothed comb can work miracles in making the dying process quicker and easier. If you're already doing something similar, do you have friend who's got some expirience with hair dye? Sometimes having someone else do it goes faster and can be easier since they've got easier access to you head than you do.
Hope this somewhat helps.