First I sanded it with some sanding paper (it read 100 on the back, so I suppose that would be 100 grit). Then, I applied a first layer with brush. And let it dry.
I guess it was too humid because one day later, things were not that dry still. I ended up leaving it hanging for 5 days.
Time to check...
and sand again...
There's some wider gap between to laminated pieces of wood (mind you, that's the part Ikea glued!). I wonder how long that body will stay in this form...