My dane (Dizzy) is about the same age and has been on 3 feeds a day for a good while now.
She's fed on Burns mostly and I water it to help prevent bloat as much as anything else. I tend to use warm water as this brings the smell out for her but then, once it's soaked it all up, I add a handfull still crunchy to give her the texture she loves :) You could try adding just a forkfull of something smelly - tuna, pilchards, tripe or even tinned dog/cat food - along with the warm water as this makes a gravy and Dizzy goes mad for it! I often use the tesco's really cheap cat food as it melts away to nothing, smells lots and has a very low protein rate.
(does that make sense, I'm loaded with the cold at the minute!)
I did try Skinners dog meal to 'fatten' her a bit but (although she likes it) the pooh to food ratio is awful and I'm sure I must scoop up more than she actually eats