I wiped inside of shell with some tung oil, put on ratchet straps, actually used my body weight to push more into round, tightened straps and then put heads on both sides and let it sit for a week or two... or more.
Love Premiers. Have a few HiFis myself. No special wires needed on these. I did replace the throw on one of mine because it constantly turning itself off, just couldn't get it to work . But wonderful drums.