Should pad be wet before applying lotion?
I put the lotion on the pads and it works great.
Can the pads be washed?
After use I rinse them with warm water & let them dry.
Would this work with oil or something more liquid than lotion?
Definitely. And has 1 additional sponges which you xn use for different products and wash.
How often should the pad be changed?
The sponge head can be replaced about every 6 months.