You ask how to do these exercises for optimal girth gains. Here’s one exercise I do a lot. It kind of combines both.
With a 70 to 90 percent erection, grab your penis around the base in a very firm underhand OK grip (your palm facing upward.)
Hold that tight so your woody gets real chubby.
Now, take your other hand and make the same grip very tightly just below the glans, around the circumcision scar on me. I play with the position a lot to emphasize different spots.
Now, just squeeze both grips very tightly for 30 -45 seconds. You can try moving your hands towards each other, apart, both pulling out, or both pushing towards your body.
This exercise has the dual benefits of getting your head real fat and swelling the shaft.
A variation I do is to take the hand around the base and press my thumb hard downward into my ligs as I use my other hand to pull upward and bend the base around the thumb. I think this affects girth and length, and seems to give me the nice upward curve I want too.