Female urethra

Over the last few years my wife has developed a fetish for peeing. It started when we used to go wild camping and has evolved over the years from a simple pee to me now blocking her urethra with either my finger or tongue. She loves it and can orgasm just by doing this alone. I let it build up pressure and then let it go. Sometimes I let some go and then block it again. She really likes it. I bought a hollow plug a few years ago to try, it was a little big and quite long. She knew I had bought it but I didn't tell her when I was going to use it. One night I decided to do just that and started playing around with it at the opening of her urethra, pushing it in slightly etc. She enjoyed it very much but as I began to push it in further she cried out and didn't want to try it again. I don't blame her to be honest, I would hate the idea, but then again I am a whimp. Lol I just think it was too big, not properly lubed and I was probably not inserting it right. She obviously likes this kind of stuff and I enjoy doing things to her so I was wondering if you guys could give some advice......... A, what is the best plug to use? Hollow? Solid? Hollow with a tap if there is such a thing? I have searched for female plugs but they all seem to be for men. What size do I need? B, is there a lube we could use specifically for this and do they do one that slightly numbs the area? I have read there is a medical gel for inserting catheters etc but I don't know which one is best. C, is there a technique for inserting it without hurting her. I am sure that if I have the right equipment and knowledge that she would try again. I might even let her do it to me if I am assured that it won't hurt. Again I am a bit of a whimp unlike my wife. Lol Tia