I'm not really well versed in underprocessed hair. Some people do a corrective or just moisterize and deal with it.
If you've gone 8 weeks, you may be in safe window..thats espcially true if you're hair is breaking from being underprocessed.
This last time I relaxed I did use quite a bit of product on my hair (phyto) oh man..I got just a lil too straight!
The key seems to be in application. If you find your hair to be more resistant, maybe you may just have to use more relaxer. Don't know if thats true for lye since I'm a no lye girl, but its definitly true for phyto, and for some ladies here, true for the no lye relaxers they use too.
I use the ponytail method to relax. I have plastic clips that I use to hold my hair into 12 ponytails then use porosity control on the previously relaxed hair, and apply relaxer where I need it. I sometimes smush it in there so I don't have to release the ponytail..hey whatever it takes man!
I can do that in 8 minutes for my whole head, and thats far quicker than I used to. Once you find a method that works and thats comfortable, its just a matter of perfecting it. Then I smooth the rest of the time, removing the clip one at a time and smoothing the section of hair, then going to the next one until I'm out of time or my hair looks like I think it should. Sometimes I go over a few minutes, sometimes (especially last time) I had no need to
I tried the 1/2 head thing because it was an emergency and I ran out of product. It turned out ok but did get a lot of water everywhere.
Self relaxing can be a very liberating experience when you don't have someone you trust to do it for you.
-A