I used to have this problem, and I found a solution that works, but it hurts like a bitch (warning: this is a very bad idea and don't do it)

Step 1: Heat up a piece of metal until it's red hot.

Step 2: Press it into the scars you want to cover up

Step 3: Scream like a bitch

It is extremely hard to suppress the urge to pull your limb away, so it helps to have a friend holding you in place to make sure it thoroughly burns you.

It sucks and takes forever to heal and will likely get infected if you don't take care of the wound, but it fucking works. Instead of obvious-linear scars, it's just one big ass flat scar. I'm no longer afraid of showing my forearms in public.