I run pull/pull on rudder and elevator on all my pattern planes.
I use nylon coated, braided stainless steel fishing trace and it is available in diferent sizes. The nylon coating prevents any wear through exit holes or if the wires touch.
Kevlar will fray at the exit holes.
Crossed or straight doesn't really matter but in alot of cases, especially on smaller models, crossing the wires gives a better set up.