I had this done back in September at a clinic in Melbourne Plaza (I can’t remember the details but can find out for you), I swear this is what helped me get pregnant as one month later we got our first positive pg test after 15 months of trying!
The procedure itself only lasts a few minutes it is like having a smear test done as they have to place a speculum inside your cervix and then they insert a small (hair like) tube into your womb. Dye is then injected and they take several x-rays of your womb and tubes to check if they are clear. The dye they used on me was oil based which is meant to have a higher success rate of women getting pg after the procedure. I found the part where they inserted the speculum uncomfortable but didn't feel either the tube or dye going in; the nurse and Dr at the clinic were very reassuring too. The information I read about the HSG said ''According to experts, HSG may flush out the fallopian tubes, possibly straighten the tubes, stimulate the cilia in the tubes or improve the cervical mucus. Doctors are currently investigating this in closer detail."
I'd definitely recommend it, good luck and if you have any questions pm me.