I have had a situation where I needed to use a multiplier but did not have room. I measured the grip length of the installed fasteners, brought it them to the workbench and used shims to simulate the grip length, torque the assembly with a wrench that could fit, marked the angle, then used he multiplier to torque to final value. I measured the angle of rotation during the final turn. Then, I was able to install the fastener in the flange, torque it initially with a wrench that fit, and then use a striking wrench to rotate the additional angle. This was for a gearbox flange on poured epoxy chocking and compressive strength was a limiting factor for bolt tension.