I've seen similar tools turned from hard wood such as red oak or maple and a rubber mallet used to shape the seal. The main idea is to form the sealing surface of the rope close to the radius of the crankshaft before installing the crank. Obviously, the ends of the seal rope need to be trimmed off flush with the block and the bearing cap so nothing interferes with the mating of those two surfaces. I use a little non-hardening gasket sealer there to prevent a seep leak at the parting line.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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