A lot of times with a question like when they will lay it is helpful to have ages in weeks as "6 months" can mean +/- 4ish weeks from one person's interpretation to the next and that 4 weeks can make quite a bit of difference in maturity of the bird.
Your little grey one is a pretty little...
The golf balls are used to show them WHERE to lay - not to induce laying itself. You don't want to use real eggs because of the length of wait you may still have (think spoilage and smelly mess if/when it gets broken) and because of mess if/when it gets broken. You can get practice golf balls...