Interesting, Nick. I use both of these techniques when Zeta-reading (whatever that is) the chapters. Firstly, I read through whatever CJ sends me. There are only occasional catches from the spell-checker, which is hardly surprising as CJ also has a spell-checker. Generally, the first read is at normal speed as I, like everyone else, just want to find out what happens next.
Secondly, I reformat the whole document to, usually, comic sans. I find it makes the differences between letters more obvious and it also shifts the line breaks to different places. This second read is much slower - I'm trying to consider each word and sentence as a collection of words as much as part of a story. Do the words make sense? Are they the words CJ thinks they are?
There can be occasional problems as, being British, I sometimes have different ideas about what is "correct". I have several American friends and relations and, over the years, I've become used to many common Americanisms but there are always new ones to learn. Sometimes I correct, sometimes I add a comment suggesting that something sounds odd to me but that, obviously, CJ's use of US English is better than mine.
In the scenes in Australia and the Falklands, I insisted on the UK spellings for words such as Harbour. I ran a few questions past Australian friends where possible to check on their usage - it's generally closer to the UK than the US but it's actually a version to itself. For the same reason, I've "corrected" some of Shane's usages away from obvious Americanisms.
After the second run-through, I make a pdf of the document and use Acrobat reader's "read out loud" feature. This almost always catches more errors, especially things like "later" and "latter" where it's so easy just to read what's obviously intended but which sound different. This can also catch repeated words and missing words which are easy to overlook. The reading is quite slow, too, which forces me to slow down as I read along and this also helps. I always try to do this final read-through in one or two sittings to help spot continuity errors.
I know CJ always insists that the final responsibility is his, but I get very embarrassed when someone points out something I've missed, especially when it's actually quite obvious...