Like many here, I use the Sailkote (McLube??). It is a great product, but unreasonably expensive. I have always wondered it something like wax might be better?
On another note, you will probably find that the thing sticks no matter what you use. That is typical of those plastic cars. Lubricating will help, but you basically cannot lubricate (at least, not well) the inside of the track where most of the friction is. I have always wanted a Batt Car system (harken). I have heard many, many people praise it - and some that had some negative comments (though I cannot remember what they were now). It is expensive... but man it looks awesome. I am trying to talk my old man into putting one his Tayana - but he hasn't come up with the cash yet!!
Brian, Please check out the Strong Track System before you decide on a Batt Car System.
Simple, clean, foolproof and proven.
Don't get me wrong. There's nothing wrong with a Batt Car System. But there are a whole lot of little parts and balls to deal with.
Regarding track lubrication; I'm not gonna say that anyone is right or wrong.
But in my experience, the problem normally isn't that the wrong product was used. The problem generally is, no product was used.
Some products leave a residue that attracts dirt. Some products evaporate too quickly. Some products are ridiculously expensive while being short lived.
You have to clean up the residue from lubes sometimes. Or if you use a dry lube you have to apply it more often.
Six of one half dozen of the other.
I have never heard of the bar soap idea, but it's something I'm am going to try.
I have used bar soap for wood screws and wax for zippers.
It's not what you use, It's how conscientious you are about using it.
A sailmaker that I know suggested that longer slugs/slides could help a little too.