Difficult, no. Time consuming...very! When straightening, start by heating the nodes and straighten them first. Let arrow cool, then go back and straighten between the nodes. Often you will have to repeat to make minor adjustments. Use gloves, and the heat source of your choice. A heat gun works great, but a stove burner or open flame will also work. For me, straightening is done over a 2 or 3 day period, letting the shafts cool between steps.
Cut your shafts long, and many spine adjustments can be made by using a larger or smaller part of the shaft.
How the shafts are oriented to the bow will also affect spine.
Most people glue a small dowel insert into the hole in the shaft at the nock and point ends.
Many use a wood foreshaft to add weight up front and to make it easier to taper if you are going to use field points or glue on broadheads.