Karmaxul

I just bought a C30 dump, 1981. He said he redid the brakes and put in a new master cylinder. The pedals spongy without a load and they work, kind of, though not how they should. I've read I may need to reverse bleed which is tough to find a connector that fits, nevermind the space to turn the bleeder. I've been told to adjust the adjuster which I have yet to find though likely is under the drum. I heard put it in reverse and go with the parking brake on. Does anyone have any advice? Can I adjust tension with the parking brake, a few clicks it, for the mean time? Thank you in advance.