Just mix some white acrylic paint into the latex. That should get you most of the way there. If the latex still looks a bit yellow when it has dried, you may need to add a tiny bit of blue to counteract the colour.
If you need to apply paint over the top, then you need to use the non-tacky version of Pros-Aide with some white acrylic mixed into it.
Thank you for the info. I appreciate it!
White acrylic paint works. Not too much, or the latex gets less stretchy, but you can put in enough to get a white colour when it dries.