In PI, use the Bristle Smear tool to feather the edges between the stripes. Then use the bristle paintbrush, white or off white, transparency = 85-95 and play around with the different texture options until you get an effect you like. Or go to the EasyPalette Painting Gallery > All, and scroll down to String. Right click > Modify Properties and Apply, change the Background color to white or cream and leave the other settings as is.
HTH,
KayLynn