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