For the majority of Post Processing in the likes of Photoshop etc, a mouse is sufficient since most of the adjustments are done via sliders or keyboard input, however for pixel level work and especially for using the lasso tools or accurate selection work and creative shading etc etc with the brush tools then the tablet and pen are unequaled. I was like you Andy when I first used a Wacom pad and pen and just couldn't get to grips with it but like most things in life perseverance and practice wins out.