Hi @Lee777,
Thank you for your question about varnishing your pine lining boards.
I would suggest using a water-based stain and varnish product such as this Cabot's Water Based Stain And Varnish, which can be purchased pre-tinted or tinted to a variety of colours.
Check out Cabots Step-by-Step Colour Guide to see what is available in terms of colour.
Start by sanding the timber with 120-grit sandpaper to prepare the surface, then give it a second sand with some 240-grit sandpaper to make it nice and smooth for your varnish.
Use a Paint Roller with a 4mm nap to achieve a nice, smooth finish and avoid any brush marks. Apply a light coat to the whole wall, then lay it off by rolling back over it all in the same direction with consistent pressure. This will ensure the varnish is even and there aren't any lines left by the roller.
Apply up to 3 coats depending on the desired colour, allowing 2 hours of drying time between each coat.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
