Most likely not. Depending on your compressed air tank, it could be designed for 3000 psi or higher. Most air compressors that the average person would use only offer up to a couple hundred psi.

In order to fill up a paintball air tank you would need a compressor designed specifically for the pressures associated with paintball tanks. Another option that some people choose to use is a SCUBA type tank that is pre-filled with air. That way with one larger tank you can fill several smaller tanks at a paintball field.

You can but you would need an adapter and it would be a direct fill. It would fill very fast depending on the size of your compressor.

NO! that will not work and you very well can rupture your tank a nitrogen tank holds between 3000 to 5000psi on average and like i said you are filling with with nitrogen not air ( although air is mostly nitrogen airis not pure and can damage your tank or horrible injure yourself