I've got two flashers and three fairies, all either male or turning male.
Adding less aggressive fish early in your stocking helps - a lot. It's certainly possible to QT a few wrasses together, should you find several that you like at the same time, and they'll likely get along as nobody has an established territory, but then you've got to introduce them to your display . . .
If there aren't any resident wrasses in your display tank, you may be OK - though I've seen some oddness. My azure damselfish, for instance, who never bother _anyone_, took a great dislike to a social fairy wrasse. I think they more or less chased him out of the tank - he left through the eggcrate. (I've got BRS screen top kits for the upgrade...)
There are some tricks that can be used post-introduction to divert aggression, such as rearranging the rockwork or temporarily placing a mirror at one end of the tank to give the aggressor something else to chase, but the best is almost certainly the "social acclimation box". It can be anything that will contain a fish and allow ample flow from the tank around it. There are purpose-built boxes made of acrylic, but other reefers have used "Critter Keepers" available at the local pet-shop and even panels of eggcrate zip-tied together. The idea is to allow the two fish to get used to one another - or at least be able to figure out if that's not gonna happen - without any damage. They get a good look at one another through the walls of the box, the resident gets to show off how tough he is ... and nobody gets hurt. Usually within a couple of days, things settle down and the new guy can be released into the display tank.
~Bruce