Multigun? Xtc snowball?
One of the translation problems here is that you were listing two events that are run by VERY different people. I couldn't tell what you meant by your post, and only after thinking about it for awhile did I go check the list of ENGC matches and discover that "XTC Snowball Match" was something that ENGC did.
Most of the people who have posted here shoot the matches that are held down in the pistol bay-area of ENGC---those being the USPSA, Multigun, and Steel Challenge matches. ENGC actually hosts a HUGE number of matches, of which those three are only a tiny part. While I'm sure that some NFOA members have attended some of the other matches (most of which are rifle matches of one sort or another) I haven't heard much from them about their matches here on the forum--and I haven't personally shot ANY of the rifle matches at ENGC. I'd like to, but I don't have time.
So----can't tell you anything about any of the rifle matches, including any XTC Snowball Match.
Here is the match schedule for 2012:
http://www.engc.us/2012_Range_Schedule.pdfIt includes contact information for the people who are in charge of those particular matches this year, so unless it is a Steel Challenge, Multigun, or USPSA match, I'd suggest contacting those match directors.
You can always contact Sandy for the other three, but several of us shoot those and post here periodically, so you can just ask here if you feel like it.
Saying all that, back to the topic: Multigun
Multigun matches at ENGC use rifle, shotgun, and pistol, and often combine the use of several guns on the same stage. "Stages" contain some "stand-and-shoot" parts, but mostly are composed of the "run-and-gun" concepts similar to larger Multigun matches held around the country (in some ways similar to the move-and-fire aspects of USPSA pistol shooting).
To compete in Multigun, you need at least a 20 gauge shotgun, a 9mm pistol (you can try it with a revolver, but you won't like it), and a semi-automatic rifle. Technically, I believe you could shoot it with a bolt-action, but you REALLY wouldn't like it.
Most people use 12 gauge shotguns (both semi-auto and pump), AR-15 rifles, and some full-capacity handgun. Extra magazines for the rifle and handgun will be necessary, along with some way to carry them.
Probably the one thing that most people DON'T think about (and need to!) is that you also need some way to carry extra shotgun shells. Some people just have a bunch in a dump pouch, which can work---but isn't really optimal. Various shell carriers are available. (Remember, you might be shooting upward of 24 rounds on a shotgun stage---can you carry enough?)
In general, for your first match, as long as you have the basic firearms and can bring enough ammo for the stage up to the line, it'll work out. Over time, if you decide to keep shooting Multigun, just like any other discipline you'll probably get a bit more competition-specific gear.
Julie already posted one video, so that can give you an idea of how it works. It is a seriously fun time.
Next Multigun match is Sunday the 18th of March---feel free to come out and give it a try. Stage setup starts at 7:15am, registration closes at 8:45, safety/new shooter briefing starts at 8:40, and shooter's meeting is at 9am.