Theres a video on U tube by Wagga - who shows how to fill the DI with resin using a small plastic bottle of Coke cut down to make a scoop, which fits into the neck of your DI tank. (search you tube for 'DI resin replacement')
Fill it 3/4 full with resin, then top up with water - the resin is heavier than water and will sink to the bottom - the water just gives you a bit of slack to put the filter & pipe through the resin.
The water won't dilute it - it is constantly flowing through the resin whilst you're working.
Dave