Now, I know I should prep at least a week before my relaxer but how?
It’s going to be a bit of an individual thing. Definitely stick with the full wash day prep beforehand.
Applying a leave in won’t really cause the relaxer to not do it’s job, to a certain extent. The relaxer will one way or another straighten the hair, although some sections may or may not straighten out more than the others, but the leave-in isn’t the sole issue. It could be what type of products you normally use, how soft or hard your water is, the Ph of your hair at that moment, the Ph of the products you use, etc.
Under processed hair isn’t inherently bad. Do your best to evenly straighten out your hair as much as you desire, but if there’s parts that are more wavy than others it’s okay. The main thing to do is to make sure your hair is as moisturized as much as possible.
I have wavy parts althroughout my hair, and my hair has been able to grow passed BCL.
I really want to do this the right way and have my hair the healthiest it can be even after the relaxer. Thanks in advance.
The “right way” is rather subjective as well. Do what you wish to allow your hair to grow how you wish. When I relax I don’t really care to prep for much of anything except making sure my scalp is okay a few days prior and dipping my ends in some type of oil or butter. Most of everything happens after the relaxer, simply because most of the prepping done beforehand doesn’t make that much a difference for me personally.
If you’re wanting to do a corrective relaxer if the need ever arises, just give your hair a good space of time in between.
Moreso than underprocessed hair, your main concern should be Ph control/correction. Do your absolute best to get your hairs Ph in the 4-5.5 range as quickly as you can. Make sure your hair is thoroughly separated as well, and relax in smaller sections.
That’s really it, the rest you can tailor to your own needs.