[Korms]

No, you don't have to use the post eraser if you are going to wait a few days before re-dying as the hair should re-oxidise over time. The post eraser is just to immediately re-oxidise the remaining colour molecules so you can see if there needs to be a further colour removal.

Also, I may be wrong here, peroxide isn't technically bleach unless it is mixed with bleaching powder. Peroxide is just a developer, you get it in normal hair dyes to activate the colour. So unless it is used with a strong lifting powder or creme, it won't be too damaging.

As for fillers, as I previously mentioned I used the Goldwell pre-colour which claims to even out the hairs porosity. As I did not dye my hair a dark colour I cannot comment on the longevity of a tint after using the pre-colour. However it is a salon brand so I assume it is of good quality.