Well, I know what that web site says about Chiggers not burrowing under the skin, but my experience with them suggests that they don't just hang on the surface waiting to be brushed of either.
I found this quote:
"They do not actually "bite," but instead form a hole in the skin called a stylostome and chew up tiny parts of the inner skin, thus causing severe irritation and swelling. "
http://en.wikipedia.org/wiki/Harvest_mite
This is a good read too:
http://mdc.mo.gov/nathis/arthopo/chiggers/
When I have had them, apart from when they have been on my eyelids, and, er, intimate bits
they have always been found at the base of a hair, like they have crawled into the folicle just a little. At the first sign of an itch a good squeeze will often wash them out where you can stick them with tape, or apply something like Prevent (Agropharm's pyrethrum based repellent).
While DEET works to keep them off, the Prevet stuff can be handy in the field if you think you have become infested. Treating trousers and sock tops with 0.5% permethrin also works very well as a preventative. Since the dry permethrin doesn't smell, you could treat your wool shirt with it. In the past, when I think that some garment might be crawling, but I don't want to wash it, I have given it a few squirts, rolled it up in a bundle in a sealed bag and left it for a few days. Seems to have worked.
If I miss that first itch and don't nail the little blighters really quick, the itch lasts the best part of a week. Catch them early and it isn't as severe, and it goes away in a couple of days.
Good luck