A good way to check live view when focusing, is to drape a large tea towel over your camera and head. This shades the screen and your eyes and makes focusing a lot easier.
When i check focus, i zoom in to the sunspot (10x) in live view. That makes it a bit easier.
Also some pre processing in registax with wavelet adjustments and then some more later in PS with the sharpening section really help those sunpots and detail to show when zoomed in.
This is just what i do and it works ok for me.
Hope it helps and if you find a better way, let me know lol
Edit- i reckon seeing has a fair bit to do with it also.