Mohair or the right kinda neoprene is good, there are some bad neoprenes though. The type found on weaver smart cinches is good. NOT THAT WHITE AIR GRIP stuff. Although for roping you may want more grip , I dotn know I am a distance trail rider.
Also sadde can make a big issue, a poor fitting saddle will caus eyou to over tighten the girth to keep it from slipping. That can cause the issue as well.
You can mail order a big tube of Chamoise Buttr from amazon
.com fo r8 bucks, will last years. It was designed for long distanc ebike riders. But works well in girth area as well. But really if you have a good fitting saddle on a normal withered horse and either a REAL, (dotn get rayon cord stuff) mohair girth or good neoprene you shouldnt really need it if your saddle fits.