First off, if you have the money just buy/use a tubular wheel set and tubular tires. It is the best option. Secondly, you can also but Stan's CX wheel set up which is a 29er MTB rim that is designed for tubless tires and Stan's system.
That said, the cheapest alternative to tubular tires is taking an old clincher wheel set and converting it over to tubless using Stan's cyclocross system. What follows is by no means the only way to do this but it worked for me.
1. Call Stan's and ask them if your wheel set will work with the system. I have a Sun ME14A wheel set that I won a few years ago and use as a back up set.
2. Take a drill with a 3/8" bit and drill out the inside valve hole. Sand it down to remove burrs.
3. One of the challenges for this and many other rims is that in order for it to seal the center of the rim has to be built up so that the Stan's rubber tire liner set up right under the clincher bead lock. What I did was take electrical tape and go around the center of the rim twice. Then I took TWO Velox rim strips and went around with those. Finally I took the Stan's rubber rim strip and installed it.
4. I went around the rim bead with a plastic tire lever and made sure the Stan's rubber rim strip was seated right up against the bead lock on both sides of the rim, all the way around.
5. I am using the Maxxis Raze tire to start with so I installed the tire and inflated it to 10 psi to make sure it held air.
6. I deflated the tire and hung the wheel from the post on my workstand (valve up). I then removed on side of the tire about 12" on the bottom, exposing the inside of the tire.
7. I shook the Stan's sealant and poured 2 Stan's cup fulls into the exposed part of the tire. I then rotated the tire around so that the sealant moved to an area where the tire was already set on both sides. Then I use my tire lever to install the tire I had exposed.
8. I inflated the tire to 50 psi and then meticulously grabbed the wheel in both hand and moved it back and forth (like a fan) revolving the tire so that the sealant was distributed.
9. I do not use soap to check the seal, I use Windex. I sprayed the Windex all around the tire/rim interface and looked for bubbles. If I saw some I placed the wheel with the bubbles at the bottom and then shook the wheel again to coat that area (Stan's website has some great video to show how this is done).
10. I then set up 2 buckets and rested each wheel sideways horizontal on a bucket for 5-10 minutes and after that inverted them.
All of this took about 2 hours. The wheels are holding fine and we will see what happens overnight. I am not using them as race wheels, only as back ups or training wheels. I am very interested to compare them to my tubular wheels.
I think this is the wave of the future but more so as UST/Tubless wheels are made more and more for cross just like MTB. I use a Bontrager tubless wheel set for MTB with Stan's sealant and have never looked back.
Tubulars are nice and feel nice but they are expensive. Stan's and tubless systems are made for the masses and I expect more and more people to give it a try.
Stan's has a nice cross wheel set for cheap and will be coming out with their own "raven" tire soon. Hutchison has a UST/tubless tire already for cross. Probably the biggest advantage to doing what I did is that you use wheels you have already and you can switch tires easily.