I've done 22 weeks. It wasn't so bad. I did it when I was pregnant. I wouldn't have even considered relaxing before my sixth month.
I did it by washing in sections and doing braidouts. This was before healthy hair knowledge, but instinctively I knew to wash in sections and braid my hair tight in sections while it was wet. I'd take out the braid and think "Hey, this looks kinda cute" and wear it that way and get compliments. I don't remember mad growth because I still wasn't treating my ends properly, but I do remember telling my stylist that "natural hair is sooo different than relaxed....it feels so strong..."...she didn't say anything.
We can be stretch buddies if you want. I am 5 weeks post and I am going for 20 weeks also. My feelings were hurt by my last stylist and I just don't want to go near another stylist right now. I also think that the only way I am going to push to BSL is to do one or two long stretches.
But back to how to:
Now I KNOW how to do it. With UBH Lotion Creme Moisturizer it will be easy. The consistency of it is very much like relaxer. When applied to my NG it smoothes it down much like the way it feels when they are smoothing your relaxer. I find that if I flatten my hair at that point with a scarf or flat braidout, the UBHLCM keeps it flat and moist. It works for me. I just can't say enough about it. By the way I have Type 4a hair with a section of 4bz across my crown from ear to ear, and my nape from earlobe to earlobe down is maybe 3a or 3b...so weird and that is the section that grows the slowest, although it never breaks. Makes getting to BSL and longer super hard.
HTH