What kind of Canon camera, and what are you using to trigger the Yongnuos? I think what you're looking for is a modeling light, so you need to know whether the remote flashes or the trigger have such a capability and whether the camera knows how to turn it on. I'd say you'll need to spend some time with the instruction manuals of all the components of your system. And there's a very good book (whose name I don't recall offhand) on using flash that several of the regulars in this forum profess to swear by. One of them will mention it, and you may want to give it a look.
Well I don't have problems with the taking photos or triggering my lights. In using a canon t3i with 3 yonguou yn560 iv and a yn560 tx transmitter to control my flashes. I also am using a seksonic flash meter and I'm getting good results. But right now with the canon eos utility I am having to drop the shutter speed way down to focus my shot using my mouse on the eos utility and then move the shutter speed back to what I want it to be for the right exposure to take my shot
People who shoot the night skies and stars do that, too. It's time consuming, but that is how it should be done under some extreme circumstances.