this is a great thread dogbone, BUT, if you're skinny...no worries dude!
just focus on your core and get ripped. if you are skinny, you are more than half way there. i know you probably don't look at it this way, but you are lucky. pushups, crunches and any other core related stuff would be perfect.
i don't want to take anything away from you're doing, but if you don't do enough 'pull' exercises, no word of a lie, my trainer says you'll develop rounded shoulders b/c one side is more developed than the other. bent over rows and dumbbell pullups are way one to do it.
i was a chubster until 2 years ago and i'm by no means ripped, but i'm alot smaller than i used to be. we do pushups every training session...and rarely repeat the same ones. we do so many types it would make your head spin (at least, it makes mine).
here's a quick link to 3 types:
http://www.military.com/Opinions/0,,Smith_082405,00.html
if anything, you should rotate the types so you don't get bored and so you work different areas (ie. triceps, vs inner and outer).
ps. one more thing: if you are looking to strengthen those arms and make them into 'pipes'......do tricep dips. why? b/c your tricep is the biggest muscle in your arm and if it's big...well, then the arm is big
🙂 plus, it's a good complimentary exercise to the pushup.
best of luck! and as we canadians like to say 'Give' er!'
🙂
Keebler