First may I say this about cock size. My fave is from 5 - 7 inches. Bigger is fine but a sweet, hairless, smooth, clear cock is so sexy.
Now, I have noticed when watching guys beat their meat, that they often loose time. That is to say loose a nice steady 'fast' milking beat. Try this, when standing around the kichen practice a good fast drum roll on the counter top. Get those muscles all tuned up for a good cock beat. Being as I play the drums gives me an advantage, but anyone can learn to beat their muscle hard and fast with a tight fist grip up to the head and down to the pubic bone.
Also, I do belive that to much play with the head of your cock, might de-sensitive it. Milk your muscle up to the head, and no more. It also looks so nice for others to see the head when jerking off.