I recently swapped my foundation brushes for beauty sponges for my travels. These things are amazing! They absorb way less of your foundations than a normal sponge or brush because of their density and the application goes on flawlessly like airbrushing. I usually bring 1-2 with me on a trip and replace them every 2-3 months.
The sponges work best when lightly damp and with all makeup, including creams, liquids, minerals, and powders.