In general, spray paint isn’t safe for birds as it could expose them to several toxic chemicals and solvents so you should avoid spray painting the basin of a bird bath to avoid potentially contaminating the water used by the birds. I would remove the top, buy a new one, and only spraypainr the outside.
It is just beautiful. I think if I make this I will put some rocks in the top basket before I glue on the top just to make it a little heavier so it doesn't get blown over with wind as easy.
Thank You for this neat bird bath idea!!! I was hoping you wasn't going to paint the inside of the pan, where the birds will be drinking from. You can still keep the plastic pan attractive by keeping the inside of the pan unpainted (for the health & safety of the birds) by putting pretty colored rocks in the bottom of the pan or a cute ceramic figurine, both can be bought at DT.. (Edited for grammar)
When my cast iron skillets get rust on them I scrub them with a steel scrub pad and a tad of Dawn soap and dry with paper towel, then wipe it down with cooking oil & let sit for 2 or 3 minutes amd then completely wipe all the oil off with paper towel or a terry cloth until you can't get any more oil off cast iron (will look dry). The cast iron will absorb some of the oil and will keep it protected.