Digging around every tree on every quote is a huge waste of time, man. Most flares are right where they should be and you just burned 10 minutes you could've spent selling the next job. If the dirt looks graded up or the trunk goes straight into the ground like a telephone pole, sure, poke at it, but making it a rule for every bid is gonna slow you way down.

Cheap discs are not the problem here, the grit is. Going from a 120 grit to a 36 grit is the whole story, the price tag barely matters in that jump. You can spend 40 bucks on a pack of high grit discs and still take forever on a trailer fender, so yeah he showed you something but it was not about the setup costing 12 dollars. Knowing your grits and swapping them instead of burning through a stack of fine ones is the real trick. Your buddy was right about your habits but wrong if he thinks the cheap grinder itself is the issue, my harbor freight one has been running for years with good discs on it.