For me personally, as a non professional, if the bolt will thread through to the bottom with little resistance, I am good. That usually means with my fingers, not a wrench. If the bolt meets enough resistance that I need a wrench, I will chase the threads until it runs in finger tight. Whether that means with a tap, a thread chaser, or a grade 8 bolt with slots cut doesn't matter much to me. It is usually just the one time. The HF taps and dies have gotten me there for years with no problems. Not bad for the $15 of so I paid for them. If the bolt happens to bottom early, I just throw a washer or two under the head of the bolt. This may not be the professional way to do it, but I have never had an issue doing it this way.

I usually make sure the head bolts will run down all the way without the head gasket or the washers in place. If they will all run down with a small amount of torque without the head gasket and washers, then I feel that they will torque down fine with the head gasket and washers. Just cheaper and easier for me rather than having a bunch of different expensive taps.

Just my