The normal procedure for catheterizing is to lubricate, but I don't think numbing gel is used as well. Just a water soluable KY Jelly is all that's needed, unless there is some sort of anatomical issue with the urethra that CM might have.
as a male - due to the greater length of the urethra - frequently for a flexi a jell is introduced which is more by way of lubricant AND mild antiseptic to avoid damage and also aid any abrasive damage - I understand that the urethra can be relatively dry internally. Also do bear in mind that at the neck of the bladder there is a sphincture muscle to close the bladder.
Clearly on mechanical common sense the more times the sphincture is forced open by a solid object the more risk of damage especially if unlubricated.
A measure of the frailty of the interior of the urethra, albeit easily expanded - there is the report of some idiot inserting the stem of a carnation into an errect penis for the amusement of his partner. This led not just to a hospital visit :-[ but to permanent damage requiring replacement of the urethra with a vein. I understand that the structure of a carnation stem is microscopic barbs pointing the right way for ease of insertion but making extraction more than somewhat eye watering.
I suggest NO ONE tries this at home - catheters are more than enough!
May I ask if you have a problem with your urethra in addition to your BC, and is that why you're asking about a numbing treatment for cathing yourself? Because as far as I know a person doesn't usually use anything to numb the area prior to catheterizing, of course when a person has a cystoscopy they (the urologist) frequently use some sort of anesthetic as the scope is usually quite large compared to when a person is catheterized. I suppose if you were male that might be another issue, one I couldn't relate to since I'm female.
The best place to get this information however would be your surgeon's office staff or the surgeon, or perhaps your primary physician if you're more comfortable asking him/her. Perhaps if you shared a little more about your situation there might be someone who could relate and then give you their take on your questions.