just changed my di this afternoon
I pour the used resin into a bucket (noting how much is in the bucket) and wash out the vessel, then ditch the resin in a bin bag and clean the bucket.
pour a similar amount of new resin into bucket add ro water (quite alot so the resin is runny when mixed )
give it a stir and pour it into vessel, when what gets left in bucket gets too sludgy add more water and repeat.
takes the ballache out of using a funnel and a scoop (as I used to)

Simon