Assuming slides are images:
Set slideExpr option to 'img'
Add an extra div with your arrow image in slideshow. Position absolute, width and height 100% and and z-index higher than number of slides. Set your arrow image, or arrow image container within div to display:none
Assume id="arrow_holder", add it's selector to "next" option.
$('#arrow_holder').hover(function(){
$(this).find('img').toggle()// show/hide when mouse enter / leave
})
You could also use animate() for effect
For 2 arrows next & prev make each 50% width