Hot water or putting something with blood on it in a dryer will set the stain and make it near impossible to remove. I use an enzyme cleaner, like the kind for pet odors and it works pretty well. Never tried hydrogen peroxide. Whatever you use, make sure it is applied when the stain is fresh for better results.
Ive tried hydrogen peroxide on blood and it bubbles up and changes color, but I've washed it out before! Usually when the fresher the better as you said tho
Ok this is super gross, but if it’s just a little blood, I’ve had excellent results using my own spit (before putting it in the proper wash lol)
As for deodorant, it doesn’t have to be denim, but using another fabric does work. I usually just use a sock or a towel, whatever’s handy when I notice it
You know it just occurred to me from your comment that they probably mean fresh deodorant. However when I think of deodorant stains I think of like pit stains and discoloration from extended use.