Good Lord man!
This sort of alchemy can get quite close to creating your own meth lab.
This is one of those times where I don't want to be involved with this site, because people are going to want to debate and the best results are really not safe.
I have spent THOUSANDS of dollars on this subject.
You have to look at all the types of plastic that go into a complex toy.
If you take it apart, they might not fit together.
If you dye it together, some parts are darker than others.
It is really complicated and you blow throu a lot of test toys.
Doing it "IN A POT" is how I started and the carnage is horrifying.
I have video of me throwing piles of clothing, toys, heads, accessories.
Half of which are now GREEN! instead of black.
I use as little dye as possible and spend a lot of time trying to leech out what I can right away.
I'd take that Japanese website with a grain of salt.
They can get better chemicals (the more toxic, the better), but
even if he could BLEACH all those different types of plastic with such perfection,
The process dries out the plastic. (Same with SHRINKING your vinyls with Acetone - which is fun, but takes half a year)
I had my share of fun with the bleaching thing, but it is pretty dangerous.
I don't even want to talk about the successful experiments, because I dont' want to encourage people.
Please be careful. Dying and Bleaching is a Highly unstable art.
Bleaching works best with a catalyst (usually causing heat to be produced in the process)
Not to mention because the Vinyl is like a sponge, the bleaching reaction can continue for months!
Harder vinyl is much more secure than Rubbery Soft vinyl
(IE the HEADS.) Use as LITTLE Dye as possible.
When in doubt, throw your dyed toy in with a pile of naked barbie dolls for 1 -3 months.
You want to make certain that everything is stable and not leaching toxins before you pass it on.
You will see the leaching problems i have been on about for years.
But then if you DYE a toy and flip it to an unsuspecting buyer within 10 months, then who really gives a rots arse, right?
It will be their collection that suffers...