THINGS YOU NEED: Dye(obviously), hair foils, ash, water, bowls, lightener/bleach and developer, latex gloves or grocery bags, more grocery bags to put over your armpits, a blow dryer, extra hands if possible.
First, take your ash, put it in a bowl, add water slowly and mix until a paste. Any ash works, cigarette, wood, it doesn't matter. You just want abrasive carbon to help remove any dye from the skin. You will get dye on your skin.
ALWAYS USE HAND PROTECTION WHEN HANDLING BLEACH, DEVELOPER, AND DYE!
If you have dark hair, you need to strip the pigment out. Whatever bleach and developer you get will have instructions, follow them exactly. Higher level bleachs means more pigment removal. Just leave some dark hair at the base, the bleach can irritate and leave blochy spots on sensitive areas.
After that, rinse it all out and let dry in a warm room. You're gonna get hot during all this, but heat opens the hair follicles and leads to the best pigment absorbtion.
Separate the hair into blocks(thin collections of hair), and saturate each block with dye. After you do one block, wrap it in the foil and pinch closed around all sides. Do this until you have all the hairs and look like you have giant bits of Christmas tinsel hanging from under your arms.
Loop the grocery bags around your shoulders, covering the armpit hair. Start blowing the hair dryer on the covered hair and get it hot. Once you got it as hot as you can handle, do your best to seal the bags around the hair. You want to trap as much heat as possible.
Let sit, with occasional reheating as needed, for a minimum 30 minutes. I like to do at least an hour, closer to two, if possible, at home for best pigment intake.
Once you've let your pigment sit, carefully remove and dispose of the bags and foils then take a shower. Rinse the hair in as cold of water as you can handle. Cold closes the follicles, trapping the pigment. You will want to use cold water every time after if you're looking to maintain pigment levels.
Use ash paste to clean up any leftover dye on the skin around the area.
Manic Panic is a semi-permanent dye, so it washes out in about 3 to 6 months, depending on how well you take care of it. If you want to get it out quicker, cheap shampoo has harsher salts that will help alongside hot water. Don't rebleach unless it has been at least 3 months, you will fry your hair if you do it too often.
I'm sorry I don't have links, and I hope this helps at all. If you have questions, or need a better explanation on something, I will absolutely do my best to clear things up as much as possible!
If you're still not feeling super comfortable, look for local trade school or cosmetology focused school! They exist, and trust me, those students love an experiment to practice on!
Sorry for not having any links on hand. I spent almost 10 years with a trained cosmetologist who often went "You have hands, help me do this, I'll explain as we work".