28-32 N.O.S. shocks

[29]

I purchased 4 nos Houdaille shocks for 1928 to 1932 models in original boxes . The oil in them is very thick like honey and one looks like it is turning to gel .
I want to empty these and refill them with new oil I purchased from Third Gen.
Any suggestions on getting the old oil out. I am thinking it would be best to have them cleared of the old oil before refilling them . Any suggestions ?