Unfortunately, for bank fishing, I agree with Sam. Sometimes you're just going to have to cut bait. By all means, try plucking the bow first; but I have had very little luck with that method -- maybe once out of every ten snags.
As to the spark plug, no reason it shouldn't work well....from a boat. I've found that my Big Uglies (same principle) work much better the more vertical the line to the snagged lure is. I've posted it a few times, but once again, I highly recommend checking ebay for Big Ugly Plug Knockers. They've saved me a ton of money AND made me a better fisherman. I have a ton more confidence throwing expensive hardware into the thicker stuff.