I've a problem that someone may have an answer for. Our search and rescue team need something to mark buildings with in the aftermath of earthquakes. We've previously used the yellow tyre chalk, but this was less than satisfactory in Pakistan last year because of all the dust closely followed by monsoon rain. Ideally, spray paint aerosols would be just the job, but we can't take them on flights and neither can we take the paint/thinners associated with hand pumps. Any ideas?