I appreciate that you don't want to make a complicated jig; but I don't recommend just doing a simple, step-through when you are dealing with a brand new bow. This is especially the case when the weight and structure of the bow remains uncertain.
I saw this method used by some Mongolians and I think it's a good one.
They found an long, narrow and flat surface (some iron railings with a flat top outside my house.) Then they found a couple of building bricks about six inches high each (i.e. the total is higher than the planned brace height), placed them atop each-other on the flat top of the railing, put a cloth over the top and placed the grip of the bow over the bricks with the back of the bow facing up.
Two people could then press down on the siyahs and use cords to tie them down around the top of the railing. The bow was then braced without a string.
After that, they made a measurement to ascertain the length of string required, made the string and strung the bow. One person lifted the grip off the bricks and took them away. The other passed one string loop through one string nock, through the loops of cord, around the brick and over the other nock. Finally, they untied the cords.
Hope this is clear.
