I can help you with the shooting thing but I'm clueless for the rest.

Basically when you feel that feeling of you penis filling up like your about to cum try to keep it in. Like when you take a leak you use those muscles to hold it in with the use of your hand.

So basically try to keep it in and carry on masturbating until you feel up to the point you cant hold it anymore then just stop try to hold it and push.

If you have to trouble holding it in with no hands you can use your hand but if you want to use the muscles i think there is an exercise called kegels try googleing it.

Good luck!

I knew tow identical twins that have your same problem. But They found that if the girl lay a diffrent way, so it didnt hurt they were okay. Hope that helps!

Megan