Is it possible/adviseable to synch LED hideaways of different brands if they all have that feature, or should I steady burn them all and use an external flasher?
The best bet would be to use an external flasher... Although the patterns may look to be they same, they might be slightly different. Also, different brands might not (and probably won't be able to) sync proberly, if at all...
Those Sho-Me LED flashers rock. Cheap and dependable. I've been using one in a light bar on a medic chase truck for over four years and it's still going strong.
Be aware that many LAWs use inline transformers and will not work on an external flasher on faster patterns, and will be slow to turn in on slower patterns, making them go out of sync.