Garb Fabric Issue

I bought some linen (actually linen-rayon blend) fabric a while back to make garb. One length was apparently without sizing, or at least didn't have much. I washed it and threw it in a nice hot dryer, and it came out fairly soft. I then dyed it with RIT dye and the result is a beautifully soft fabric in a lovely medium greyish blue shade.

The other, much longer, length came from a bolt that must have had an enormous amount of sizing applied. I've washed it twice now, using hot water, detergent and a generous dose of fabric softener added to the rinse water, dried it in a hot dryer and it is STILL stiff and scratchy (although admittedly, somewhat less so than when I began). I was hoping to leave this fabric white and use it in chemises but there's no way I want it next to my skin the way it feels at present. Is there some way for me to soften it up, or am I going to have to break down and dye it for use in outer garments, in the hopes that the dyeing process will soften it up some? And before anyone suggests it, no, it's too stiff and scratchy for me to want to tough it out over a few/several wearings in the hope that it will soften up on its own. I'm sure it would be entertaining to watch me trying to discreetly scratch and squirm at an event, but I'm not planning to give everyone the pleasure.