I'm about halfway through the Proofread of Doom. I'm using the same approach I took with Journey to Altmortis, which was prolonged and dreadful but did eliminate almost every single error.
The proofread's done in two stages. Firstly, I read each chapter on my Kindle and mark up any errors. That's not too bad. Secondly, I read through the work again, as carefully as I can, whilst updating it on the computer.
That doesn't sound particularly difficult, but it takes ages, and I'm well aware that's the last stage before it gets published. So, I spend a lot of time on it, my eyes go fuzzy fairly quickly and it's easily the most difficult (in a non-creative way) part of the whole writing process. (For those interested, the most difficult creative challenge is creating plot twists, because it's easy to make them either deus ex machina or predictable, both of which are a bit rubbish).
I am hoping to get Sir Edric's Temple out this month but, as I'm a one-man band, I can't guarantee it. That will be for the electronic format. The physical format will be released later, but still this year (hopefully).