Should I look for another plumber? Are the guys being honest with me?

Are you kidding? Maybe not.

If they have other work to do, any mud is too muddy. Would you work in a
muddy crawl space if you had a choice?
Look for someone who need the work more, offer to pay him a premium, or wait
until he feels like doing it. It is unreasonable to expect someone who is
busy to give mud a priority for no reason.