Best type of paint for cardboard?

[RoastieToastieReastie]

We have a huge cardboard box in going to turn into a puppet theatre for DD and need to paint it red. I've tried with her poster paint before on cardboard and it need so many layers it'll take me a lifetime. I've used art acrylics in the past which work well but are expensive.

Would regular wall emulsion paint work? Or maybe a spray paint? Any recommendations please before I go and buy something tomorrow

I would do an undercoat in either white or grey (standard paint for walls etc but use a waterbased low fume one) then use acrylics on top or a tester pot of normal paint for walls . Acrylics can be expensive from an art shop but it is possible to find them elsewhere cheaper

Thanks RB. The box is huge (taller than DD who is 5) so I will need a lot of paint. I have some white emulsion in the shed I could use as an undercoat then get a one coat emulsion in red (or maybe just two coats of red?). I think acrylic will be do costly for such a huge size...

I know you mention it'll be a theatre but we had a similar large box which we acquired with the new dishwasher, we turned it into a den. Painting it never occurred to me at the time. I glued coloured paper on all the walls both inside and outside. We bought the paper rolls from Lidl, they are like wrapping paper but larger in diameter and also slightly thicker than standard wrapping paper, so they are durable. We had bought it in bright yellow, red and blue so we used different colours on different walls of the box. Also put battery operated tiny Christmas lights which we had bought from wilko for -not sure how muc exactly but very, very cheaply.
So, you could always cover with a paper. Ikea used to sell such plain, large, strong paper rolls too.

Interesting idea Ilike. I will see what (if anything) we have locally.