I recommend a shampoo that is formulated to help prepare the hair for heat styling. so Salon quality shampoos and conditioners.
Keracare, Design Essentials, Kera, Nairobi, Elucence, etc..
If you have a lot of build up, or only use a sulfate shampoo once a month, then a clarifying shampoo would be needed.
Next you need a Moisturizing sulfate shampoo.
Cones are needed to provide protection when heat styling.
Generally certified cosmotologists would not recommend adding oils to your conditioners. The conditioners are meant to work alone during heat styling. When you add product for slip, you are creating a coating, that could cause your conditioner to not work effectively in protecting your hair (hair could burn/heat damage), therefore oil and heat doesn't mix.
This is why it's so hard for naturals to get salon results at home. Too much product, not using products correctly, not properly removing buildup, and using super low heat.
And to be honest you take a risk with getting a silk press. Your hair is not naturally Silky, so you are going against the grain trying to achieve something it wasn't meant to do.
Naturals that like their hair to revert back shouldn't focus on relaxer straight results. That's what relaxers are for.
