no offence to your dad, but follow the haynes manual or something. this is the second time ive noticed hes tryed to dissuade you from doing the job properely in favour of a method hes been "doing for years"
i only usually have trouble gettng the full angles on the very final "after warming" sequence. use your discretion.
as for the "why cant you just do them up to X torque" question. nearly all the force applied to a bolt is used up overcoming friction, and that friction will vary wildly depending on preparation, lubrication etc. theres no way to accurately predict how much friction will needed to be overcome and then how much torque required to get the correct clamping force on the head gasket. hence the angle method.
Oiling the threads is a BAD idea, if you're gonna use the stock torque sequence.
The manufacturer's angle sequence is meant for clean, dry threads and brand new bolts.
Clean all threads very carefully and blow any excess crap with compressed air (after you've covered everything around)
You don't need really an angle tool, if you use a long breaker bar you can estimate where 90 degrees are, can't you? That's good enough.
I've torqued enough to know that oiled/greased threads need different settings for the same effect.
Any serious bolt manufacturer will give you different torque settings for dry and oiled threads. If nothing is mentioned, it's implied that the threads are dry. If there is any doubt, I'd contact the manufacturer, as this can lead to damage...
The same torque reading on the wrench leads to different tensile stretch forces on the threads
dry threads will have the least forces
oiled threads will have more
greased threads will have the most
Dry threads will be the least reliable though, that's why precision fastener manufacturers prefer oiled or greased threads - but they do provide different torque settings, which allow for these conditions.
i understand friction and torque wrenches, but i dont see the relevance. head bolts in this instance are angle tightened, turning from point a to point b, in my opinion making that easier is paramount. not only will a lubed thread be easier to turn, there will be less shearing forces on the thread itself, lee chance of recking the thread.
to be honest most of it is squeezed out and left on the block face. and if the hole was previously dried you still have the cone shape section at the bottom of the hole to play with. (if you imagine the block would have been drilled originally)