I'd suggest checking manga forums or dedicated Bleach fan sites. They often have detailed breakdowns and recommendations on where to pick up after a specific part. Sometimes, the author or official sources might provide cues as well.
White Cat Blocker was a common type of bleacher that could be used to effectively rinse clothes. The white cat's Blocker contains hydrogen Peroxide-a powerful bleacher that can remove stains from clothes and make white clothes cleaner. However, it was important to note that White Cat Bleach was only suitable for white cotton, hemp, and terylane, and their blended and chloride-bleachable clothes. If it was misused on colored clothes, it would cause the color of the clothes to fade. If the clothes are dyed, it is recommended to send them to a professional laundry for re-dyeing. In general, White Cat Blocker could be used to rinse clothes, but one had to pay attention to the material and color of the clothes when using it to avoid adverse effects.
Honestly, I don't know when the TYBW manga starts. But you could search manga databases or ask in manga enthusiast communities to get the details you need.
The popularity of white bleach fanfic is due in part to the rich world of Bleach. Fans love to explore different aspects of the white - colored characters and their stories. It gives them a chance to expand on the original narrative.