At the moment in Chiangmai, V.velutina is a bit of a problem but I have found that if you spend an hour, early one morning swatting all of them, (and they are very easy to swat), then predation is greatly reduced for quite a few days afterwards. I think this may because the pheromone trail that the hornets lay between our hives and their nest, goes cold without returning foragers, and it takes them time to relocate the food source and re-establish the link. What does not seem to work so well is swatting a few, now and then.
If you do use a trap, I think its better to use a meat bait, (they like pork), rather than a sugar based bait. We want to trap the ones that are foraging for animal proteins, not sugars.
MMJ100's colonies under siege may eventually be weakened to the point that the hornets will arrive on mass and then the colony may be lost. However, you can help the bees a lot by feeding a tray of sugar water every couple of days.