Even if a little coolant finds its way to a blind hole, no harm, no foul- - - -it can't go anywhere else. I like to use a little anti-sieze on head bolt threads, and just a dab under the head of the bolt. That's more for uniform torque than coolant sealing, but it might prevent a leak by promoting better contact between the threads in the block and the head bolts. Some shops where I've worked used brush-on Permatex as a thread lube. I don't have a problem with doing it that way. Dry-torqueing any kind of bolt results in some torque loss from friction, so any lubricant, even 30 weight motor oil, will allow more accurate torque.
Jerry
