how to wash rayon-linen-cotton blend to prevent shrinking

I just bought a rayon-linen-cotton blend top that fits perfectly. However, many of the reviews of this top mention shrinkage after following the washing instructions (cold wash gentle cycle, line dry).

Will handwashing prevent this?

And is the additional instruction to "reshape while damp" aimed at preventing shrinkage? If yes, what steps to do I take to reshape it? Should I measure the current length/width and then stretch it to that length on a flat surface? At what point does it need to be removed from the reshaping surface and transfer to a drying rack?