There was a fad. in the Seventies I think, to put sponge under the wipers and oil it (you would see this being done in the parc ferme at the Fort) but I don't know if this stopped due to bad results arising or just CBA.

Sounds like a way of covering up you have leaky seals to strat with.

Why not save £16 and just buy one of those neoprene compression things you can get from the pound shop that are supposed to be worn when you have an injury, you could just cut it up to size and sow it back up. 'Simples'.