I am building an 8x 10 shed for use as workshop for my daughter in CA following directions in book by david stiles. The roof will be a minor challenge. I am planning on 8 inch overhang on eaves and will add 8 inch overhang on gables for appearance. My question concerns cutting the bird mouth on rafter trusses so they sit squarely on wall.

Daid Stiles says to cut smple 2x4 rafters at 66 inches with a plumb line at approx 40 degrees. He gives measurements as to where to cut birdsmouth but my attempts w jig saw left much to be desired. Here is my question. I have a workbench which is precisely 8 feet long and my shed will be precisely 8 feet wide. It seems to me that I can rough out the sample truss attaching the tops with a gusset and using a collar tie for rigidity and then just hold the sample truss ( with a helper) against my worktable to determine exactly where the birds mouth cut will go, trace it, cut it with a circular saw and my sample is complete. Looking for someone who has been there and done that to comment and set me straight. I think I will upgrade rafters to 2x6 to facilitate cuts w circular saw. Rafters and wall studs are 16" OC.. Wall studs are also 66 inches but the use of a collar tie 11 inches above wall height results in ample headroom in the shed

Last question re sheathing and shingling roof. I am 70 and do not relish heights or climbing on a roof. Should I use roof jacks nailed into rafters for a secure place to sit while nailing sheathing and shingles. This will be my first roof ever. Can these roof jacks be rented or must i buy same

thanks