The bolts will be much harder to take out than put in. Generally oil will work its way to where the threads are, and over time it will coke up. It acts almost like glue.
I don't remember exactly what you have done to the engine up to this point, but I'll make a few suggestions:
Clean threads = accurate torques. Remember the factory put this thing together with everything clean as a whistle. If you are re-using your head bolts, clean them thoroughly! Lots of brake cleaner/carb cleaner or whatever that will break down all the old oil and coking. If new, just make sure any rust prevention coatings are removed. I can’t remember if they are just oiled or coated with anti rust liquid.
Clean the threads in the block thoroughly! These threads are nastier than you think. Lots of brake cleaner/carb cleaner and a bottle brush, rags, whatever. Just make sure if you use a bottle brush with wire bristles that they are fine, and preferably a soft material like brass. It will take a long time, but getting the threads clean is worth it IMO. Make sure you blow out the holes with compressed air to ensure no grit or leftover rag/paper towel bit remain. Clean the threads until a clean head bolt threads in and out nice and smooth with no resistance. These two steps ensure that the clamping force for each head bolt is as close as possible.
If you are using stock head bolts and head gasket (which I think you are?) you should follow the factory manual procedure. It probably tells you to oil the threads, which you should. Honestly, you should always lube the threads, and adjust torque to compensate if need be. If the manual says to oil them, and specifies a torque, use the torque they give applied using the pattern they specify. I recommend that after everything is clean, you put clean oil on the threads of the bolts and run them into the block a few times to make sure bolt bolt and block threads are nicely lubricated. Try not to oil *just* the bolt and put into the block with dry threads.
If I have time I’ll try to find the factory procedure/information.