My girlfriend's sister had a baby and her mother wants to make some sort of yard sign to put in their yard announcing the baby. She's gonna make a pattern of a stroller with a baby in it and wants me to cut it out for her. I'm looking to make something cheap but durable to the elements. Her other sister is having a baby in August so it has to last long enough to be re-used. What would be a good wood to use for this project? I'm thinking something that comes in a 4x8 sheet like plywood, particle board, etc. I'm not real sure how well these would hold up in the rain and elements though. This will also be painted. I'm figuring I'll tell her mom to use some type of outdoor grade paint, but is there something else I can use to seal this off after painting to help make it last even longer?