Alright, after playing around today for about 2 hours, here's what has come of my search for fuzz in my BB/B3K rig. The two fuzzes I have are the MXR Bass Fuzz Deluxe and EHX Deluxe Bass Big Muff. Very different fuzzes, but good in their own ways. Ok, here goes.
I love my B3K into my BB, and after switching them around first, that's how they'll stay. Definitely. Their settings are my OD sound, so they're not being changed. Typically, I've been using fuzz after all my dirt, as a sort of intensity ramp up. Solo, it sounded great. In the mix, I got buried instantly. So after some suggestions from TB people, I got to moving my fuzz around in my chain. First, I kept it last, and just changed fuzzes. I got a nice setting to test out on each fuzz.
In the last position, I felt the Muff was good. It's a bit darker, and didn't overpower the other effects. It had a low blend as well, which is what I want. I don't want tons of fuzz since my whole spectrum is distorted at this point. It was nice, thick, and warm, but with some bite from the BB. I liked it. The BFD took over the signal in this position. Everything was just high gain fuzz. No real remnant of my previous pedals remained in the signal. No good.
Then, I tried them both in front of the dirt section. The MXR sounded pretty good. The B3K tamed the shrillness, and let it go through the chain. Not a bad sound for high gain fuzz with other dirt. Unfortunately, that's not really what I wanted, so while it might be useful to me, I let it go. The Muff simply did nothing for me in this position. The darker tone being tamed by the B3K made everything muffled. Not good, and not at all what I wanted. At this point, I thought the MXR was going to win this battle.
Finally, I tried them in between my B3K and BB. I would never have tried this without it being suggested. Lo and behold, that's where the magic is! I tried the MXR, and again, it hijacked the signal again a bit too much for my liking. But the Muff shined! It was livened up just a tad by the B3K, and then it did its Muffy magic on the signal. But, instead of just being warm and thick, it had just a little bit of crunch from the B3K owing to the low blend I was using. Perfect! Slightly less present in the mix, but a great fuzz tone that I tested on some of my material and it would certainly work well. Then, I turned on the BB. AMAZING! Got that fuzz, and then it just rips with the BB engaged. That makes it cut like crazy. Gonna try it at practice Tuesday, but I have no doubts.
Now, here is my rig, and I have no intentions of changing it for a LOOOONG time: Bass > B3K > Deluxe Bass Big Muff > Blower Box > iStomp #1 (changes) > iStomp #2 (Envelope Filter) > FDeck HPF3 > MXR Bass Compressor > MXR Smart Gate.
Gonna cross post in the DG forum as well since I got some suggestions there too.
Thanks everyone!