I have no idea about the paint, but with sand my answer would be none. Sand can cause impaction which can turn fatal. If you have an ADULT beardie and choose to use sand, use dry sifted playground sand. Under no circumstances should calci-sand be used asit clumps together in dragon's stomachs. Babies should not be kept on any sand because they lick everything and can become impacted much more easily. I would recommend you use tile, repticarpet, papertowel, or nonadhesive shelf-liner.
Hope this helps,
Sara