"How do other custom knife makers handle the situation where people want to "touch" products first?"

About the only way practicable to do that is to set up at knife shows. I am leery about sending a knife to someone to 'see if I like it.' I've never been burnt, but I've come close.

I once loaned a knife to a person to test. It was a really nice knife, mirror polished 154 CM, a four inch clip point blade, tapered tang and an ivory Mircata handle that I had a ring neck pheasant in flight scrimshawed on, at considerable expense.

The idiot went on vacation to a beach and used the knife to dig clams in the sand. Needless to say, it was terribly scratched and dull.

He wanted to buy another knife, but not that one. I wouldn't sell him one of any type, at any price, and I have never spoken to him again.