Some things that you can do when grooming your horse are to work on making sure your horse accepts being touched all over, you should be able to touch everywhere on your horses body, this is something to work towards if your horse has some iffy spots that he doesn't like having touched.
You can also work on basic ground manners, making sure that your horse is respecting your space and will move over or forward or back when asked.
If your horse has issues with picking up his feet and/or holding them up for the farrier, you can also work on this during grooming when you pick out his feet.
Lots of currying with a rubber curry, brushing using natural bristle brushes, and finishing off your grooming session using a real sheepskin mitt, lots of time spent rubbing your horse with the sheepskin will make your horse shine. Also, good nutrition and deworming as needed will keep your horse healthy from the inside out which is the most important step to a shiny coat.
I don't recommend bathing with shampoo on a regular basis. Shampoo strips the natural oils from your horse's coat that make him shiny. In the summer if your horse gets sweaty when you ride him it is a good idea to hose him off with plain water to get rid of the sweat so he won't feel itchy, attract bugs and fade in the sun.
If you are grooming your horse on a daily basis and grooming thoroughly, his skin and coat shouldn't need to be washed with shampoo very often.