-Making sure hair is clean, I double shampoo (triple if necessary). The shampoo does not have to be stripping. Since you have a keratin treatment, your regular maintenance shampoo should be fine. A clarifying shampoo will strip away the keratin which is counter productive . Avoid sulfates/sodium chloride at all costs.
-Using a deep treatment, Macadamia oil mask is HG for me. Only takes 7-15 mins to do the job. I find that oils and heavy products in general are very hard to fully rinse which actually makes it difficult to create shine. So when going for straight styles I always go very light handed with treatments/deep conditioners.
-If you heat style, I found that using a creamy leave in combined with a serum (with silicones) before blow drying creates so much shine. Using a keratin infused leave in will create so much shine as well as prolong your smoothing treatment.
-Using a finishing serum, john frieda skinny serum is my favorite from the mid shaft to the ends. Very careful to not use too much because it can make the hair look piecey.
I also found that been heavy handed with product before heat styling does not necessarily create better results. It's tricky to figure out the middle ground where to get just enough product.
-a Boar bristle brush is very good at distributing sebum from your scalp to your ends. If you mainly wear straight styles, this is great for getting a light detangle between washes.