What is the best way to get rid of frizz?

I am 43 and have longish hair which I dye with a semi-permenant dye every few weeks. My hair is naturally straightish but gets very frizzy. At the moment I wash and condition about 3 time a week but don't use any other products and usually let my hair dry naturally. I am a bit wary of getting straightening irons in case they damage my hair. Are they good or are they damaging? Would blow drying work or make my hair worse by damaging it? Are there any styling products anyone can recommend for regular use?