I actually at first didn't realize you had to do this, When I first got my two guys, I brought them to a small animal vet, who never mentioned it. When a vet that specialized in small animals moved into the vet we go to for our other pets, I went to her, luckily she had chins and told me about this, and did check and found tigger did have one......now this was two years later, so thats two years without checking for one and only tigger had one.
After that i've been nervous about checking, but it just takes some time, first time I was really nervous but after a bit, was able to check.
I also noticed, they aren't checking themselves alot like they use to. I think its good advice to check when you see them checking themselves out, or just once a month.
But you'll get use to it, I'm still getting use to it, but it gets easier.