Hiding wood grain or texture before repainting

[DIY1st]

Hi all, looking for a bit of advice.
Re-Painting a fireplace front/surround. It is wood and would guess its pine because can see knots bleeding through in two spots. But the wood has a lot of wavy texture or pattern showing through old paint. Its not stain but uneven texture. I attach a pic and hope that will help to explain. At another spot you can see and feel the pine's ring-like pattern too - this doesnt bother me much. But this wavy texture seems like wood piece wasnt plained before installing!!

I was thinking of Zinsser BIN primer (my most used tin this year because this house is full of pines!) then a surface filler to even out texture and sand to smooth surface? Which surface filler to use though?

I have:

• A large tub of Gyproc EasiFiller Finish (used it with good results on un-even wall surface, dries a bit slow but super easy to sand - loved it) - Can I use this?
• A small tub of Polyfill multipurpose (good too but more difficult to sand)
• An unopened tub of Ronseal Woodfiller (never used it so dont know how easy it is and if I would be able to get good results with it)
• An unopened tube of Polyfilla Wood filler (never used it)

Many thanks

 

[Mr Chibs]

It looks like it’s slightly concaved as well?

Think I’d start with a sanding first, p60 wrapped around a piece of waste/gutter pipe, if this works, just move to 120 grit and finer if needed.

 

[Tigercubrider]

Another option could be something like a reed moulding if the area is the correct width?(or close)