Injection technique - invicorp

[Never_Enough]

I believe the injection technique is the same regardless of the medicine but I just wanted a little help.

Had a poor reaction to aprostadil 2.5 mcg back in Oct probably due to low dose and improper technique... Doc waTched but didn't do it himself.

At a home setting I can grt a semi before injecting so knowing location should be easier.

Assuming I am loooking down and holding my penis out how far down the shaft should I inject?

I know the needle should be at 10 or 2 but how do I ensure it doesn't go too far in?

Thanks.

[Never_Enough]

Just to add.

A guide on YouTube mentions pulling the foreskin down if you are uncircumcised.. But when I do this I have way too much skin and it creates folds over the area to be ijnjected even if I hold the glans and stretch it.. Why does the foreskin need to. Be pulled down?

Thanks