Wear on the timber coating happens to all coatings after some time and you'll notice it first in high trafficked areas like in front of the sink. You can attempt to spot treat those areas by sanding back to fresh timber to remove the dark discolouration and applying a polyurethane floor coating.
Whenever trying to fix an individual section of the floor there is always a risk that the repair will be noticeable. You should consider if it would be in your best interest to sand and coat the entire floor. If you are planning on selling then a fresh coating on the floor would certainly be appealing to buyers.
When floors are badly damaged, I cannot see a way or think of a basic coating product that will improve them sufficiently. You could coat over such floors as they are, but the results will not be particularly impressive and it may cause more work at a later date. If you have a lot of discolouration, any product or coating will seal the surface, but in doing so trap the discolouration within it.
In such a case, you are looking at a full resurfacing. Sanding a timber floor seems a daunting project, but the benefit to sanding before a new coating is that there will be an incredible difference in appearance, not only looking great but it will add value to the property.
There is a range of products which can be used on wooden floors for their everyday maintenance and to extend the lifetime of coatings applied to them. Some of these products include O-cedar 450ml Clean And Shine Timber Floor Cleaner, Long Life 1L Timber Floor Cleaner, Cabots 1L Floor Clean and Feast Watson 1L Floor Clean. These products are specially formulated to work on hardwood floor coatings, provide a streak-free finish and to rejuvenate timber floors prolonging their life.
For a scraper to use with timber putty I would recommend a plastic scraper, as the last thing you want to do is damage the timber floor more with a metal one. A handy hint is that you want to remove the excess putty prior to it going hard. Once it has become solid you'll need to sand it flat and you don't want to be sanding the floor.
The greyed timber look popular for the last eight years is achieved by lime-washing over a lighter coloured timber like Vic ash. Since your timber has some strong reds in it, the outcome of using a lime-wash would be unknown. There are a couple of ways to do the lime wash. The first being the limewash by itself and then CFP to seal it or the one-step limewash and polyurethane coating. These products can be tinted to different shades, and the catalogues in-store will show you what is available. Alternatively, there are paint products like Feast Watson 4L Satin White Floor Paint available. All these products require you to sand the floor back to bare timber.
I trust you'll find these step-by-step guides useful:
Whilst there's a bit of extra skill, time and effort involved, you want to sand back floors before refinishing/resealing them. You'll be wasting your time and money otherwise. There are many tips and sayings in the DIY/trades world. One perfectly suited to this situation is "If a job's worth doing, it's worth doing right." - ProjectPete