Here are a few recruitment tips I have found to work in starting 4 groups.

First, one of your best recruitment pools seems to be wargaming (or even role-playing) clubs - you can usually contact them through shops that sell the equipment and games for wargaming and role-playing. What I've done several times is contact the club president (or whatever) and convince him to invite your guys (or just yourself, if you're starting a group from scratch) along to display what you do. You'll probably get about 30 enthusiastic newbies, which will shrink to about 3 in the next 3 weeks.
But those 3 will be KEEN.

Go to your local library and offer to give a talk on the Middle Ages. Take your best gear along. Get books out of the library (or from your own collection) with good pictures that involve and interest people. Make sure you take leaflets, plus pen and paper so you can get their contact details. Give a brief talk on some area of the Middle Ages that interests you and that you know a fair bit about. Let people ask lots of questions and touch the stuff. If they have questions you can't answer, compliment them on asking a very good question, admit you don't know the answer and offer to find out for them.

Arrange to put on a display at the next opening of a movie about mediaeval themes in your area (we did it with the Lord of The Rings, with VERY good response). And take along leaflets and (even more important) a pad and pen to write down names addresses and phone numbers. Follow up within a few days people who respond , invite them along to your next training day. (Be gentle with them - start them slow. A lot of these people are too young to fight, and you'll have to get them involved with other aspects of the club until they get old enough). Make sure you keep the parents on side - they CAN be your best allies, as
they see their kids getting involved in something that, if not conventional, is at least not hanging around in malls, smoking dope, massacring their schoolmates etc, and has some older people in the activity who at least SEEM mature (you and I know different). And its even educational. And sometimes you get recruits from among the parents as well.

And do your training in a park that is VERY visible to passing public. This is one of the other main recruitment pools, and produces a steady trickle, but the people who come up and ask "what are you doing", often follow up with "I've always wanted to get into this stuff, but never been able to find anyone to do it with." Put a helmet on the guy's head, give him a shield and sword to hold, and GENTLY take him thru the basics.

And, oh, yes. You'll get a lot of people who are into being elves, warlocks or whatever. Some will leave when it turns out this is not what they were after. Others will need to be gently brought to see the True Faith, adopt more authentic practices (no, sorry, no horns on the helmet, no fantasy swords). This is the area I have the most hassle with, having been doing this for 15 or more years, and it's hard to remember how bad I myself was then. I tend to be an authenticity fascist, and I cringe when I see the crap newbies come out with. Be tolerant, and gently guide them into the True Path. And give them the correct information BEORE they make anything. That way (a) you don't have to cringe every time you see it, and (b) they won't cringe every time they see it  two years from now.