Hi Steve.
I've had Colin share a photo of the flyer in the Bust@ group on Facebook (monthly). While a paper flyer I great promotion at an event for bags and handouts (and hopefully doesn't just going into people's bins), using a photo of a flyer to promote on social media doesn't really grab the attention of many people and get people engaged and talking about it.
The last post in the group on November 8th for example has a reach of 751 people (out of 4.4k members), just 8 reactions, 5 photo views, and one comment thread.
Salute that happened last weekend for example didn't really promote (as usual if I'm honest) and I found many people who didn't even know it was going on.
To really get people attention now you need to try and work social media more, and I don't mean paying for adverts as they often miss the target audience. But posting from a dedicated page with interesting posts to get people talking, using good quality images (actually upload the flyer image that was use to print the flyers for example), stories, and hashtags is all part of it. Use Instagram too.
As for competition rules; publish them in advance so people can plan entries. Don't tell people to phone someone (especially if that's a personal phone number which bring all sorts of security issues anyway). Give information so they don't have to ask and have an info email or tell people to message via Facebook. Don't let people invade your private time.
If this just seems harsh, I'm sorry. But I'd rather see the hobby community thrive than see empty halls where traders are paying to hopefully find new customers and organisers/staff have been busy setting up. The promotion is vital to attract people and so many shows I see really hold back on it.