I use strips of duct tape and coat everything with baby powder.
I just had an insanely ridiculous round of flats on a brand new bike with alex rims. Now, I love alex's and have only had great luck with them so this was hard.
What it turned out to be is a flexible plastic rim strip that I suppose is 'sposed to be more bulletproof than rubber, but after about a flat every 2 days I was trying anything. I pulled the hard synthetic rim strip out and replaced it with very carefully stuck 1/2" duct tape strips, baby powdered, all is good for months
