ahh yeh I learned my lesson just last week. I cant answer anything as far as bass because I'm a drummer but this was our first time playing in front of an audience and first time with a soundguy. We played a benefit show for the humane society so it was just 6 sets of 3 songs per band and our guitarists and bassist used some other guys amps.
#1 make sure you got what you need in your monitor, when you do soundcheck if you need more volume, make sure you let him know.
#2 either bring your own gear or make sure everything is set correctly after someone else uses your gear, dont take anyones word for it.
#3 it's usually never as bad as you think, I thought with all of that we sounded horrible and after the show people kept coming up and telling us we sounded great
we used the other people gear for simplicity and everything was great during soundcheck but we didnt realize that we needed to speak up and tell the soundguy what we needed in our mix. So after the soundcheck I'm saying that all I was hearing in my mix was a bit of my snare and vocals, couldnt hear the guitars and bass at all. Too late and the soundguy said he would try and push my levels up for the show.
we're all used to rehearsal where everything is blaring but it's totally different when you're on stage, you have the mains out front and the amps are all miced and running at low volume. the FOH volume was plenty loud but I couldnt hear a damn thing and my bassist said the same thing, he said "man, i look down and I can se the strings vibrating but I couldnt hear anything except your drums"
the other thing, if you're sharing gear, make sure you check that the levels havent been changed. our guitarist plugged into a marshall half stack during soundcheck and the levels and tones were just right. He was told to just remember what the main volume was set on and at showtime just plug in and set the main. He did exactly that and when he hit the first chord it totally drowned out the rest of the band. Also on our second song when he changed settings on his pedal it pretty much came out like mud, luckily i knew what he was playing and started the song right on time but the first 2 measures were totally unrecognizable.
good luck and I hope what we learned helps you avoid the mistake.
but since I have no experience with them, is there anything I should be careful of when playing through them with technique wise, amps settings? Any input would be gladly taken 
. The one thing I noticed the most was the sustaining notes. Maybe it was just the subs I was playing through but they're not exactly the quickest so quick notes were tending to mud up the sound. 
