Mikey, I very much doubt your mates compressor would produce anywhere near enough psi.
Compressors which are suitable for paintball usually run into the thousands of pounds and arent the general compressors anybody would have lying around.
You may have spent 500quid on kit, but you'll soon realise thats the tip of the iceberg
A dive tank can be found for around about #100 or so if you are lucky and they can be a good investment if you are going to use it alot.
Otherwise you're stuck with getting a fill when you go and play next.