Joyce from Rigid Heddle Weaving.com has a great tip online for warping a loom on constant tension, just by yourself.
It uses friction instead of weight to create tension. The warp travels over and under round rods and the friction gives it even tension. The warp that still needs to be rolled onto the loom can just hang there, totally free and with weird uneven tension. It’s here, on the left. In the middle is the reed, having no function at the moment. To the right are four rods, fixed to two small weaving sticks with rubber bands. At the far right I’m rolling the warp onto the loom, without any effort.
It worked like a charm!