I have a love-hate relationship with No-Tubes.
As a shop-rat I would mount No-Tubes conversions using an air compressor. Ninety percent of the time it works. For the other 10 percent, I would remove the valve core and use a schrader air chuck to get the maximum air volume into the tire fast enough to seat the tire without having sealant spew everywhere.
Done, ready to ride. Well kinda.
Tubeless works well, when it works – we're talking about non-UST here. Flat protection and better ride quality are why I do it. The downside is that on the trail you may not be able to re-seat a tire. So you throw a tube in and you're back to square one.
A few days ago I mounted a new pair of Continental Mountain Kings – 29x2.2 – on my Stan's 355 rims. I try to not rely on a compressor; I want all my setups to be "field serviceable" come race day. The Mountain Kings fit loose enough that they wouldn't seal with a floor pump.
Luckily there's a quick and easy fix for many loose fitting tires, just build-up the tape. I use 3M strapping tape, cheap, readily available and strong. A few layers on the rim and everything seated with a confident "snap."
Tubeless Tips: To ensure your tires hold air I've found the following works well.
1. Once inflated, hold the wheel with both hands and tap the tire against the ground while rotating the wheel. This ensures the bead is seated.
2. As soon as you've got the bead seated and the tire appears to be holding air put your wheels back on your bike and take it for a couple of laps around the block. This helps the sealant cover the entire surface of the tire.
3. If using tubeless conversions with non-UST rated tires do not exceed 40 PSI. If you inflate standard tires set up tubeless much higher than this, the force exerted on the tire can exceed the tensile strength of the bead. Boom! the bead fails and you are left covered in goop, with a ruined tire, looking like an idiot – been there.
More tubeless setup info can be found here.
It seems everyone who runs tubeless conversions has their own approach to making it work. One of these days I'll get around to brewing my own sealant.