Is there a way to get the light plug to slide in and out easier?

What I do, especially in the winter months, is give the trailer recepticle a good shot of WD40, getting rid of any corrosion build up.
Then I put a small dab of dialetric grease over the holes in the tractor plug. Usually there is a bit of a residue, so just spread a VERY light coat around the first couple of inches of the plug. Slides in and out easily after that, just remember to use gloves.

 

Same here

 

I'd avoid WD40 as it attracts crud.

You might want to look at the prongs inside of the plug. Each of those posts has a split down the middle of it, and if some are splayed open too far that might make it more difficult to plug in.

But I'd be more worried if it went it too easy, because then it can come out too easy too!

 

Clean the tractor side using Scotchbrite pad. That'll remove all the buggers and make it smoother