Truthfully: It stings for about 1-2 seconds, and then the pain goes. You get a bruise the next day, but it only hurts if you press down on it (like a normal bruise would). It's honestly not that bad.
What to wear:
Make sure you take gloves, these will protect your hands as when you get shot on the hands it hurts the most. :P
Wear a long-sleeved jumper for maximum protection, make sure it's not to tight though otherwise you'll get too hot.
Wear any trousers, I'd recommend some that are easy to move in though (baggy). They will also most likely get dirty. Don't wear jeans.
If it's wet, wear shoes you don't mind getting muddy.
Most of all, have fun. And don't be afraid to ask someone to help tighten your mask; there's nothing worse than running around with an uncomfortable mask on!
If you want maximum protection you can go to the store you can buy a paintball vest. Wear baggy clothes, they will take most of the shock away. I would highly suggest something that will protect your neck and gloves for your hands. It hurts for a few seconds then its over till the next day. You will have some welts.
The pain is more shock to be honest, and you get used to it easily.
As for what to wear, wear baggy, light clothes that cover your skin. The bagginess will reduce the chance of a painful shot, but still allow you move freely. Also, no joke, wear the most padded bra you have! From people telling me it's not fun when you have no protection there. Wear old trousers (again preferably baggy - NO JEANS) old joggers would do fine. For your shoes, if you are in the woods, wear some plain walking boots with good support. You can wear wellies, but they are hot and restrict your movement. If you are on flat ground/indoors stick with light, dark coloured trainers.
Hope this helps and good luck!
wear Jeans! & a long sleeved shirt, if not you'll get. bruices on your arms...
And it doesn't really hurt only like for three seconds.
The next day you will be in pain though