I agree with recessivegenequeen, it’s not a necessary element during dilation exercises, but it DOES help.
My therapist learned me that when you’re excited, your body prepares itself to accommodate a penis, so masturbation before/during dilation WILL actually help if you’re able to do that! She did prohibit me from getting orgasms though, so getting sexually excited was okay, but that’s where it should end. As a previous poster wrote, an orgasm does the opposite and makes your vagina contract, renders the opening smaller and more difficult to penetrate. So that’s definitely not a good idea during dilation.
I have heard there are also therapists who integrate masturbation into their treatment plan, together with Tantra, breathing exercises and relaxation techniques.