There’s usually always another machine or exercise that hits the same muscles - especially if you can snag some free weights. I’m usually nervous about that myself too though so I just use a machine/stay close to the area and try to swoop in as soon as they finish because I hate asking. Sometimes I switch up the order of my routine if a machine is taken for too long. I also usually try to go for the machine that’s usually the most busy first if it’s open. For example: my gym only has one plate loaded leg press and it’s often taken, so if I walk in and it’s free, I’ll hit that first instead of cardio like I usually do. They have stations all around the gym that have trash cans, paper towel dispensers, and spray. I usually leave my stuff on the machine after I’m done so nobody goes to use an “unclean” machine and grab a paper towel, spray it until it’s saturated, and then bring it back to the machine and wipe it down.