The insertion of objects by the urethra usually is done with Hegar sounds or probes because they are easy to clean and have different size. A paintbrush is not the best for sounding but the handles of this paintbrushes are conical and it can help to stretch the pisshole.
Female stretching the pisshole with 3 large brushes handles conical penetrating it very deep until bladder while her cunt is open wide with a speculum for more easy insertion.
It can be a good idea to train the urethra stretching it for more huge objects but the most important and necessary is to have a lot of care with the cleanliness of the objects you want to insert and use a good lubricating gel based on water.
She keeps her pussy open with a speculum to have better access to the hole of the urethra and be able to stretch the pisshole more easily dilating slowly while maintaining a vibrator on the clitoris that provides a greater pleasure and multiple orgasms.
Using brushes to stretch the female urethra can be good ida and is a method that is often seen in extreme videos of women masturbating the peehole to achieve pleasure and new methods to get orgasms and different sensations.
She enjoys introducing deeply the 3 handles of the paintbrushes at the same time to feel since her pisshole stretched when enters the thickest part of the handles inside the urethra which does her rub the G-spot and simultaneously she puts a powerful vibrator in her clitoris to feel a double pleasure and taking an impressive orgasm.