It is a lot more complex than can be explained in a pamphlet I guess. Purification is right, "blessing" is a Catholic word, so not so traditional. It is more like a messenger, smoke goes everywhere and 'Shpeming [[up in the sky) to carry our prayers to the Creator.
Some more teachings on the Sacred Herbs:
Sema -- In addition to the Eastern Direction and the first aspect of life [[the mind), Sema represents the first part of the day, the first season [[spring), the first stage of one’s life, the first clan [[the eagle), and the Oriental race.
Giishik -- represents the southern direction, the middle part of the day, the second season [[summer), the second stage of life [[youth), the second aspect of life [[the body), the second clan [[the deer), and the Anishinaabe nation.
Mshkwadewash -- represents the western direction, the evening or setting sun, the third season [[autumn), the adult stage of life, the third aspect of life [[emotions), the buffalo clan, and the black race.
Wiingashk -- represents the northern direction, the last part of the day [[the night), the last season [[winter), the last stage of life [[the elder), the fourth aspect of life [[the spirit), the bear clan, and the white race of man.
I pulled this from Kenny Pheasant's wonderful website because it is so concise. I <3 Kenny Pheasant.
http://www.anishinaabemdaa.com/ceremonies.htm
Note the representation of the four races, race being a rather foreign concept, but representing the four recognized general skin colors. If you go around the medicine wheel, the colors coincide as well, Yellow in the east, Red in the south, Black in the west, and White in the north.