I've had strike brandings done and also brandings done with a cautery pen.
There's much more control with a cautery pen.
BMEshop used to sell them for about $100 plus tips that you use once and dispose of in a sharps container, preferably. If you're really set on doing it yourself!
I gave myself a nasty 3rd degree burn with a lighter, a quarter and a magnet (I think, I was 18...) Don't do that.
Caring for burns isn't easy. I could barely move after I got a branding (cautery pen) on my stomach. You have to be really careful, they're 3rd degree burns and could be very dangerous if done improperly or cared for improperly. A 3rd degree burn leaves a scar pretty much no matter what you do to it. I irritated my brand with steel wool and then cleaned it well with antibacterial soap afterwards. (This isn't always necessary..)

• First-degree burns are usually limited to redness (erythema), a white plaque and minor pain at the site of injury. These burns only involve the epidermis.

• Second-degree burns manifest as erythema with superficial blistering of the skin, and can involve more or less pain depending on the level of nerve involvement. Second-degree burns involve the superficial (papillary) dermis and may also involve the deep (reticular) dermis layer.
• Third-degree burns occur when the epidermis is lost with damage to the hypodermis and possibly muscle underneath. Burn victims will exhibit charring and extreme damage of the dermis, and sometimes hard eschar will be present. Third-degree burns result in scarring and victims will also exhibit the loss of skin hair and keratin. These burns may require hospitalization.
• Fourth-degree burns damage muscle, tendon, and ligament tissue, thus result in charring and catastrophic damage of the hypodermis. In some instances the hypodermis tissue may be partially or completely burned away as well as this may result in a condition called compartment syndrome, which threatens both the life and the limb and the patient. Grafting is required if the burn does not prove to be fatal.
• Fifth-degree burns result in hypodermis being burnt off, leaving blackened muscle, tendon, and ligament. Fat, nerves, veins, and arteries have been destroyed and the burn area is paralyzed as a result. Amputation or grafting is required if the burn does not prove to be fatal, depending on the amount of bone envolvement.
• Sixth-degree burns leaving blackened bone and damaging marrow tissue, these burns will definitely require amputation.

So.. BE CAREFUL!

I would definately recommend going to a professional. Not that I haven't dont it to myself before, but its been a long time. You are always better off going to a professional where you can have it done in a sterile environment and to ensure it comes out just right. Now, regarding aftercare...

remember use discretion when selecting your method of aftercare as the more irritation you create on the wounds the higher risk or infection and increased and prolonged pain. P icking and scrubbing your wound can illicit a stronger immune response, giving your body more opportunity to react or over react and create more scar tissue. Please be aware that every body will scar differently and occasionally no amount of skin irritation can guarantee a raised scar.

Method #1 , fastest and least painful healing method.

• Clean the wound with soap and water twice a day and apply a bandage until the wound is completely healed.

Method #2 , slightly prolonged healing and can be somewhat painful

• Clean the wound with soap and water twice a day
• While cleaning remove any scabbing that may have formed using either clean hands or a toothbrush soaked in peroxide.
• Apply a bandage until the wound is completely healed.

Method #3 , longest healing, very painful, increases risk for infection, not always recommended.

• Clean the wound with soap and water twice a day
• While cleaning remove any scabbing that may have formed using either clean hands or a toothbrush soaked in peroxide.
• Apply an irritant such as sesame oil, 3% hydrogen peroxide, lemon juice or salt.. This will aggravate the wound and ideally increase scarring. Many irritants can be applied and their results will vary.
• Apply a bandage until the wound is completely healed.

For smaller pieces ø plain glycerine soaps should suffice
For larger pieces or people with weakened immune systems it might be a good idea to use an anti-bacterial product such as Technicare, Dial Anti-bacterial soap or even tea-tree oil soap