By thinning it is a lot easier to work with but a couple points
1- I put about a qt of water for a bucket 1 time you don't add every time you use. But you re-stir every time.
2-When you seal the bucket even if it's over night wipe down the inside with a wet rag. then put the plastic that came on top back on then the lid.
3- When mixing use a drywall mixer blade not one for stirring paint.
4-When mixing use a variable speed drill and go slow to med. if you go too fast it puts air in the mix and you will get what we call fish-eyes or small craters in your finished product.
I should have added this to the first one, the amount of water added also depends on what mud you are using all purpose, light weight, ect. After stirring you should be able to load your knife turn it over and the mud not fall off.
Hope this helps.