When you get more experienced and work with bands that don't suck this problem along with a host of other ains such as the keyboard played noodling while you are working on a ringing tom.
You don't know until you know is my new motto. I really had no idea jist what a bunch of shitty ham and eggers (love this phrase DB) that were employing me until we started getting larger calls. Pro's are 1000 times easier to run than a cover band in a bar.
By no means is it a panacea. Diva's can be a royal pain too.
Don't waste your time trying to change them either, they won't listen and don't care. You are just delaying them gettimg another drink, toke, bump or whatever they are after. My apologies tonthe 1% of bar playing covet bands that don't act like this.
Here is what you do, treat cover bands as a festival mix. You can rough the gains in then as they set you verify tje input so you are line checked. If they want a sound check go through the motions however you should have a good mix on the first song. Next song you set dynamics then fine tune eq. Your changes should be subtle but deliberate and advance the mix without jarimg the audience. Your mix improves as the band warms up and gets in the pocket.
For me I got spoiled running steady sound for a group of seasoned musicians(the leader owning a sound co. of his own)it was a breeze.Worked a few larger shows(with his co.) doing staging and a few at FOH.
Then as I got venturing out looking for work(after that bands end)on my own system(my budget limits me to bar bands,I simply dont have the money to expand out),I discovered a few things LOL Drama queens and "Ham and Eggers" LMAO(I like that term..haha).
Another erk of mine is...I start each channel with fader down,then pfl channel on meter,have them play instrument,I gain up quick,then slide channel up and start EQ and dynamics. But I never get more that two kick hits(I start mix with kick)befor they stop and say "nothing is coming out" or kick kick...'is that good"?....kick kick
"is that good enough?" Noooo....keep going...LOL
I love hearding up a band for sound check also....they were all on stage a second ago when I did monitors,but now drums are set and bass player and guitar player are at the bar or in the car or in miami beach tanning. "Soundcheck" meant everyone stay till its done. LOL
Dont get me wrong there not ALL this way,but sometimes I want to bang my head on the mixer I get anxiety when things become a cluster.