Most websites say fabric can be kashered by putting it in a washing machine set to 'hot'. How would would one without a washing machine kasher fabrics? By Hagalah, washing with yad soledes bo water or another method?
From the OU:
Magen Avrohom (O.C. 442:19) writes that a tablecloth can be kashered for Pesach if it undergoes a thorough washing with hot water and soap and is beaten. Igros Moshe (Orach Chaim IV:106) writes that today’s home washing machines, when run through a hot cycle with detergent and agitation, satisfy all these requirements. Rav Belsky, zt”l held that towels made from polyester and other synthetic materials can be kashered in this manner. However, one must inspect the cloth or towel thoroughly to make sure that no chametz remains. It is therefore, better to buy new towels for Pesach, and only use washed tablecloths if they are covered with plastic.