With the foam running the full length of the tube, things can get kinda tight under the charging handle. In fact, depending upon which tube you have, those thick bike grips won't let the charging handle fully extend.
Besides, the Exile Machine rubber cover was only $8.24 shipped, arrived in 3 days, and is WAY more durable than those bike grips. Unlike the open cell foam of the bike grips, the Exile cover will not absorb water or chemicals. Plus, it protects the end of the buffer tube from dings. I don't see any reason to go the bike grip route when a much better option is easily acquired for the same price.
Mine slid right on my Spike's tube with no effort, yet is not coming back off without surgery. No personal grooming products needed.