Do you/Can you only get it on Ebay,not locally??
At a guess I would say that there is enough in one tube for 30 or more applications,after all you only need a little more than the equvilent of a grain of rice ..
Anything by Artic Silver is pretty much the builders standard. You can't go wrong, and you should be able to buy it from any neighborhood PC shop, and many retail electronics stores like Frys, Best Buy, Radio Shack. It's not hard to find and only costs a few bucks.
You only need a RICE GRAIN SIZE DROP to do the job. Too much is as bad or even worse than not enough when you go to install your heatsink. Remember that!
And 1 tube will last most people the rest of their life, literally. The only thing that happens is it can get dried out after several years.
As for application methods, they address it in the article for the main types of HSF bases out there. With how little you need to use, any tube you get will be enough for a dozen computers, so you're covered for 3.