Best way to straighten curly hair?

When you get out of the shower blow dry it using the cold air stream function in your blowdryer, that helps to calm the frizz, or buy anti frizz conditioner.

Of course you can flat iron it but that can really damage your hair.

In the hair isle of your local supermarket there should be lots of products to straighten it, eg. hairspray, antifrizz conditioner and shampoo, special hair treatments etc.

look in the woman's section, there's usually a wider variety of products.

Also comb it intead of brushing

I would recommend that you blowdry your hair with a brush. I am assuming since your a guy you have short hair and so that will be easy for you to do. For the frizz try oil, I use coconut oil but you could use hair gel, wax anything like that really.