If you want to lose a lot of height in the PA28 'in an emergency' then I don't think side slipping's the answer - you just don't lost height fast enough. I've had a badly rough running engine and came in high on the approach - thought I could slip it in once I cleared a town, but it didn't come down. Had to put in some big S turns and aircraft responded well. Remember with high angles of bank in the glide you need to increase your speed.
The technique of dumping the nose is okay, it relies on parasite drag stopping the speed running away - works brilliantly on something like the Arrow.
One trick you can try is coming in too low on the glide. Assuming the aircraft's clean, keep your speed up and with 20 ft to go dump all the flap - that'll make you balloon and clear a hedge or obstacle. Works really well in PA28.