When using concealer instead of base

I'm thinking of changing my makeup a bit.

Before, I used to apply sunscreen and then immediately apply cushion foundation.

I'm planning to apply concealer all over my face as a base. Should I use a sponge or pat it on with a puff? Which would be better? Also, after applying the base, would it be better to just sweep powder over it once, or use a pressed powder? I want a thin look, so I'm thinking of just using concealer as a base and stopping there, but I'm worried it might look messy due to oiliness.