Hold on, I don't agree. Those old tricks can be hit or miss. Like when you try to smooth wood with a piece of glass, it might scratch it. Sandpaper is cheap and lets you pick how smooth you want it. Using shortcuts often leads to bad results. We have better tools now for a reason.
Have you ever tried smoothing wood with glass before dismissing it? I used a broken bottle edge on an oak table leg and got a finish that felt like polished stone. Yeah, sandpaper is reliable and cheap, but that glass trick worked because I went really slow and kept it wet. It's not for every job, but sometimes those old methods come in handy when you're in a pinch.
Yeah gibson.morgan saying old tricks are hit or miss is fair. I used a glass shard on a walnut chair arm once and it worked great for a tight curve. You just gotta know when to use it.