Dealing with filler before lining walls

[deano34]

Hi

I have removed a picture rail from some walls and there is a wooden batten where this used to be. It's nailed into the walls flush so I have filled with tetrion but a yellow rust colour is seeping through.

I plan to line the walls with 1200 lining paper but am worried the colour will come through after painting.

Can I prime/seal the filler with anything? Stain block, oil based undercoat?

Any help much appreciated .

 

[Zampa]

Oil based undercoat will be fine

 

[deano34]

Lovely, thanx