Can I use a wood preservative on my shed then paint it?

Many but not all wood preservatives contain a small amount of wax or silicon to offer a degree of weather protection, this can be problematic if looking to paint the shed and especially with a water based exterior paint. Wax and silicon free preservers are available such as Barrettine Premier Universal Preservative and Sadolin Quick Drying Wood Preserver. These can be applied then painted over when fully dry.