There definitely is dye to do fabrics by hand but from past experience, I definitely wouldn't advise it for something as big as a sofa cover! I tried dyeing a bedspread and did it several times over, but it still came out patchy and uneven. For something as huge as a sofa cover I think it needs to be machine :(.
I'm going to try dyeing ours as soon as I get my backside in gear to get the dye. If it works you're welcome to come and use my front-loader! :)
I would like to have a go at this but I do not have a front loader washing machine. So far I have only seen Dylon colour for front loaders. Does anyone know if there is colour Dye out there to dye fabric by hand or in a top loader?