From what I have read on these posts and my personal experience, you probably won't get out any "ropes" (mucoid plaque) if you just do the MC. The B&Ps will remove ropes.
If you have eaten shortening, margarine, and/or white flour (which is 99% of us at some point in our lives) you probably have them. They are like dark rubber innertubes lining your intestines. Each time you ate junk food, you added another layer. They hold toxins and block your intestines from absorbing vitamins in the food you eat.
I didn't see any ropes until 2 days after I started on the B&Ps (Day 20). Yes, it's true, your weight (numbers on the scale) will not fall off as quickly as before the B&Ps, but that is because your intestines are filling with the psyllium (which holds alot of water). So the fat and toxins are still being eliminated, but your body is holding more liquids.
Keep the bigger picture in mind.
You want to be healthy.
To do that you need to remove the toxins from your body, starting at the cellular level. As the toxins make their way out of your body, their passageways should be cleared often (by you showering, deep breathing, and moving your bowels).
You could just do the MC, and lose alot of weight. Guess what, you will gain back some water weight (as your intestines fill with food again). But if you still have the ropes inside, your body might start gaining fat again to buffer itself from all those toxins the ropes are holding.
So if you clear out your intestines with the B&Ps and the MC, you are doing a double-whammy to those toxins (cleaning your cells and your bowels).
As you get closer and closer to that goal of being healthy you will:
Repair most (if not, all) damage done to your organs from a poor diet.
Bring your body back into proper balance (between good and bad bacteria, cholesterol, hormones, etc.)
Lose excess fat.
And hopefully, your brain will understand how what you eat effects how your body will respond.
If you do the B&Ps, just make sure you are eliminating at least once a day.
Some people feel more comfortable doing the salt-water flush to control the timing of their elimination. (Although your bowels will need to learn to work on their own again after the MC; another reason I like the B&Ps.)
Should you realize by the evening, that you haven't eliminated well that day, go ahead and do a salt-water flush or prune juice or even just warm water. Sometimes that (constipation) is caused by not drinking enough water throughout the day, so drink more the next day.
I did 3 B&Ps a day. Some super-humans do 5 a day, but you really have to drink ALOT of WATER.
So after you end the Master-Cleanse (with the B&Ps) this time, and you change your diet (to healthy food and rare/no junk), you will continue to lose excess fat (because your body won't need to build up a buffer against toxins). And the next time you do the Master-Cleanse as maintenance (in 6 months?) you probably won't need to do the B&Ps and you'll probably only need to go 10 days.