Blu tack residue and stains

[Lilliput]

My dd has gone off to Uni so I thought I would decorate her empty room. But, oh my god, the damage from blu tack!!!
Firstly how to I get rid of the small amount of blu tack residue and then how do I prevent the grease marks coming through the fresh paint.
I can see why landlords ban the stuff!

I think that I read somewhere that a dry piece of white bread rubbed on it will help

We used this, great stuff

https://www.toolstation.com/zinsser-cover-stain-primer-paint/p56164?store=CP&utmsource=googleshopping&utmmmedium=feed&utmcampaign=googleshoppingfeed&mkwid==dm&pcrid=558676913905&pkw=&pmt=&gclid=Cj0KCQiAzfuNBhCGARIsAD1nu-84udtpYZlxsYjHWDsWFJqKhz0IHqRWnr2c64ieguHuXDLJF4Fn7waAoWDEALww_wcB&gclsrc=aw.ds