Hi @Shazart,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Is it possible to get some photos of the stairs? This will help our members offer advice specific to your project. Let me know if you need a hand uploading images, I'm more than happy to help.
Your choice of product will come down to personal preference of how you want the stairs to look.
If you want to go with a more natural timber look you could use Intergrain 4L UltraDeck Slip Resistant Decking Oil which is a lightly pigmented, slip-resistant coating for use on a variety of surfaces including timber steps. This will bring out the natural beauty of the timber while offering increased slip resistance.
If you want to go with a painted finish, a suitable exterior paint such as Dulux Weathershield can be tinted to your choice of colour and an anti-slip additive such as Berger Jet Dry 300g Clear True Grip can be added to the paint. This will give you a great amount of slip protection with a wide variety of colour choices.
The process for applying these coatings would be much the same, sand the timber back to achieve a nice consistent surface, thoroughly clean the stairs to remove any dirt or debris, and then apply your coating following all manufacturer's instructions.
You might like to check out How To Restore Wooden Furniture and How To Sand A Deck for some similar examples you can apply to your project.
Let me know what you think.
Jacob
