I've taken about 20 of these apart and can't for the life of me understand the hitch you described.
lube the assembly with like KY or some other non petroleum jelly.
get about seven different screwdrivers of varying blade width and work the spring in gently.
alternatively. go to a plumbing supply and get an Oatey block off plug, there's a bunch of different kinds but many have a screw that allows the plug to be easily removed so you can add water and sand.