doors hard to close, have tried lubricant

[thefranks5]

I know this sounds really elementary, but .... I have three Toyotas, and the doors on two of them -- both sedans -- are closing really hard ... On two of the doors you have to use two hands to close them. I've tried applying a silicone type lubricant, but it doesn't seem to do much.

Has anyone experienced the same thing, and found a solution? I'm thinking there must be something more than just applying lubricant, but would like to avoid disassembling the door, if at all possible.

Thanks in advance for your insights