Work one manageable area at a time such as four square feet.
How to floor varnish.
Let the dust settle vacuum it up and then wipe down your floor with white spirit.
If your old varnish is flaking off use a floor sander to sand back to the bare wood.
If you want to change or improve the floor color apply a stain.
Choose an interior wood stain based on the color you desire and the type of hardwood flooring you have.
How to prepare varnished floors lightly sand your floor with 120 grit sandpaper.
Use your brush to apply the new oil based varnish to the floor.
Apply in sections which are no larger than 4 to 5 square feet.
This will ensure that the varnish looks natural.
Depending on the condition of the floor you may need to start sanding with a coarser sandpaper.
Start at one end of the room and sand with the grain.
Use a long handled roller to spread the varnish first in the same direction as the grain then across.
Fill in any gaps in the floorboards if you need to or want to.
When making the strokes try to follow the wood grain.
Apply the stain with a foam applicator pad in the direction of the wood grain.