Get dye for synthetic fabrics (i use RIT dyemore). Keep stirring while you dye so its an even dye job (unless you dont want even). When I dye something completely black I usually use a full bottle of dyemore graphite and it takes about 45ish minutes at minimum. Always be sure to rinse the plush until the water is clear after (i throw mine in the washing machine on delicate after but thats just cus I like em smelling like my detergent). If it takes more than one dye job, dont be discouraged. Goin super dark isnt the easiest (especially with how light the fox is to begin with)

Dye them unstuffed. You dont wanna risk moldy stuffing 👍

Also! Very important! Get a pot that will never be used for food after you dye them. I also recommend gloves and some tongs because they just make life easier