I don't use stretched sprue for antennae; I find guitar strings much more realistic in size, material, appearance, and flexibility.
But, this process can be used to create just the right diameter of plastic round parts or bits for various applications. Also useful for creating bodywork beading or trim.
Besides antennae bases or miscellaneous shafts or attachment posts, the stretched sprue can be used to plug holes. Insert the stretched sprue until its diameter is snug in the hole, wipe it with some liquid cement, then clip off the excess on either side of the plugged part. Sand smooth and presto! Hole plugged with little muss and fuss.