I wet-blend a lot and never use a wet pallette, so YES, IT\'S POSSIBLE! Wouldn\'t want to do it without retarder, though... But as Shaz pointed out, you\'ll need to be rather quick.
If I\'m not mistaken, the wet pallete mostly just helps keep your paint \"open\" on the pallete longer. While this means your paint is a less prone to dry, it is not essential to blending, I think.
My pallette couldn\'t get any drier. It\'s a white glazed ceramic tile. Yep, retarder is the business, but a little tends to go a long way, as I learnt the first time I used it. I squirted a little retarder onto my pallette, and used an old brush to mix it into my paint. Painted up the weapon on what I was working on, then went to do something else. Long story short, It was still wet 12 hours later.