Try Goof-Off, you can get at Home Depot and Lowes, but test it first on an inconspicuious spot, as it may remove your finish, but it's supposed to remove marker and crayon. Good Luck!
No, in fact the wax can ruin the polyurethane finish. Clean the floor with a good wood floor cleaner. Do not mop with water.
Polyurethane applied to a floor is virtually never sprayed. It is generally applied with an absorbent pad, frequently made of wool or a synthetic.
Rubber casters are better for a hardwood floor as they will not scratch the wood surface and not leave black marks on your floor.
Screening a floor means a light sanding, just to take off the polyurethane. Coating it, is to reapply to finish.
About $80 to rent a floor sander and polyurethane is about $25 a gallon. So depends on how big of an area
Say it was high gloss, if the wood soaks it in deep and you only put two thin coats on it will not shine like it should. Because it should shine a lot. Can depend on how much gets absorbed by the wood.
Polyurethane coatings do a number of things. First, they seal the pores of the wood making the wood unable to absorb moister and thus preventing rot. Secondly, urethane allows the floor to be cleaned more easily by providing a smooth surface. Third, they help to prevent scratching or gouging of the floor by providing a 'slippery' surface that objects can slide across. Fourth, some urethanes have a built in UV inhibitor which can keep the wood from discoloring.
Polyurethane becomes sticky because it takes an hour or longer for the oxygen-induce crosslinking to occur. Polyurethane is a varnish used on wood.
Varathane is the best product available to the general public. The finish is very durable and dries relatively quickly.
Yes, you can.
hair spray
Polyurethane is usually used over stained or unstained wood to protect it from water and damage. It is a sealer.