It is surprisingly easy and effective. And I must say, it looks better than the white flyer stands from GW. If you're going to do it yourself I'd have 2 tips:
1) Don't put on too much cotton, keep a margin between the edge of your base and your model. I've covered mine completly and now they constantly get stuck on everything. Including eachothers clouds, somehow.
2) Spray one of those protective coats on it, like GW's ardcoat once it's glued. It keeps the cotton in somewhat of a fixed shape and acts as additional "glue" so you're less likely to lose bits & the aircurrents from the spray help make them look more like realistic clouds.