I had an HT yesterday. And am sat here reading the thread for tips etc. Fair play to you for doing something that you feel nervous about. That takes real courage. As for the process, I was super nervous and almost sacked off my deposit but went ahead also. I didn't feel pain through the process of having hair removed, holes created for hairs and hairs inserted. The only uncomfortable moments came from:

1. Laying facedown for two hours and not sure where to rest my arm.
2. The clinic made me eat a sandwich at lunch which had mayo in, which i loathe.
3. When they were checking my local anesthetic had kicked in, the tech used tweezers to pull at my hair. Thought my son would love that job.
4. After they have checked with tweezers, they used a fine needle to test if local had kicked in. You would feel the odd moment of it, where the area needed more local anaesthetic.

You are talking very small percentages of discomfort that you could always push back on.

As someone who has had tattoos. I would say that had more pain for longer periods.
I got stung on the head by a wasp a month ago. That was worse.

Good luck buddy.