I've tested my cat tons of times and for the first time just last week I had a gusher.
In my case though, I warmed the ear too much and then hit the vein. Even though my lancet was on a shallow setting, it just went crazy.
I didn't put anything on his ear because he probably would have licked it and rubbed it and maybe make it bleed more. I just kept constant pressure on it until it stopped bleeding. He had a small bruise but is now gone after a few days.
He probably doesn't have any discomfort. If the blood is in his fur, try to wipe it out with a warm cloth. My cat just sat there asleep while his ear was bleeding like no tomorrow.
You'll get the hang of how long to warm his ear for approximately before testing and that's how I control the bleeding.
I gave your other thread a quick read, you are using a lancet right? Is it on a shallow enough setting that it's not piercing through his ear? I hold a tissue on the opposite side of the ear before I use the lancet, so I can press it firmly against his ear. I use a One Touch Ultra, with the Delica lancets. At the setting of '3', it went through his ear because I could see a drop of blood on the tissue. At a setting of '2', it didn't go through his ear, but I had to warm his ear longer before taking a poke at it.
I know it's scary, but the bleeding is stopped, and the bruising will go away. It was difficult for me to test at the beginning, but I got the hang of it after a while. Sometimes I still have difficulty though, just in getting enough blood or maybe my hand slipped and i lanced too close to the outer edge of the ear!
Don't worry! You'll develop your own technique and get better, and kitty is fine!