In my experience, the rule about not discussing sex before a date is more about being respectful. I think it's more to do with the fact that providers don't want to be treated like free phone sex operators.
For something like this, I think that there are a lot of providers who would be happy to assure you in advance that they'll help you test-drive the new equipment. I'd read the board posts of some ladies, particularly but not necessarily on the over-60s board and get a sense for who might be understanding and open, then drop a couple of ladies a polite PM.
One thing that you might consider is registering with P411 and putting it in your profile. Only providers that you share the link with will be able to see it.