Yes I filled it with water first! I intend to live a bit longer... I did think about the grease gun but as soon as it springs a leak I couldn't pump it fast enough to keep up any sort of pressure. Some use an old grease gun submerged in water for poor mans hydroforming. I will see how things go with the 2000psi waterblaster and go from there.do you get all the air out? I think a grease gun puts out more pressure.
"A high-pressure grease gun delivers pressure up to 15,000 psi. " Google
if you need that much. that is a lot of grease to fill up your pipe.
I have a friend who did the same thing for the flying surfaces on his piper cub.For angle adjustment on my 3 blade prop I downloaded an inclinonmeter onto my phone. Free app and works accurately enough on a 500 mph tip speed.
Just a thought.