Manual stretches: How hard do I pull?

I’m sure this has been asked and answered here before, but searching did not bring up any usable results for me. If someone can direct me to a thread, I would appreciate it.

If not, here goes: I have been PEing for about three weeks now and when it comes to manual stretches I am not sure how hard to pull. Of course, the answer lies somewhere between hard enough to make gains and not so hard that I injure myself.

Is there a sensation or feeling that I should be looking for? Do I go for the burn like body building? Going for the burn feels like I stand a good chance of injury. Does it just take time and experience to figure this out?

Thanks,
-Vegas

Pull so that you feel a stretch. Dont’ worry about how hard you pull as long as its not hurting you.

Warm up though.

I pull at about 70% strength in the beginning and at 90-100% in the end and I can (could 5 months ago) do a clean military press from my chest with 80-90 kg - 1 rep.