They don't typically work. Given the fact that Guatemalan indigenous peoples have lived in obscurity and poverty for hundreds of years, I would submit that any purification rendered would be (to put it generously) symbolic at best. Guatemala's political past is riddled with tin-hat military dictators, Marxist crackpots, U. S. puppet-governments, and smatterings of leaders "of the people" who typically fiddled while indigenous factions burned. Literally.
If I read things correctly, this Juan Tiney has actually done what LDS missionaries to the region have been accused of for generations: exploiting the Maya. If you remove yourself from the less rural regions of Iximche and Lake Atitlan, it doesn't take long to find settlements of Maya who not only have no idea who George W. Bush is, they also couldn't care less. George W. has no effect on their ability to plant and harvest corn or beans. George W. is not the reason why they need to move their adobe huts from one corner of their land to another. All they know (or care) is that they have work to do. Politics is for those who have time on their hands.
Yes, I'm sure that Mr. Tiney was able to find very sincere Mayan "priests" (shamans, really) who are eager to purify the land after Bush leaves. Just be sure to ask them how life has been since they last purified it after one of their own government officials visited the place.