Painting OSB

Morning all. Hopefully someone has come across this before..

I have just clad the inside of my outbuilding in OSB3. Wall sheets ate butted together and behind it sits a vapour control layer.

I now want to seal/caulk the joins and paint over. Gaps vary from tight upto 5mm.

Thoughts on what I can fill with without causing the OSB seams to swell... then I need to consider what type of paint I should use. I've heard something acyrlic/oil based is best?

Thoughts?

For anyone that finds this thread by a search I opted for a specialised paint bt Zinsser. Zinsser Allcoat Exterior Matt (Tinted).

Yes for 5L it may feel expensive but goes on great. I got my man cave painted, ceiling and all internal walls (building size 6m x 4m) done in one coat. One more coat may enhance the colour so may do it at some point.

It has a great matt finish and with the right method got into the OSB grain great.

Hope the post helps someone.