This may help I did mine 5 years ago
http://www.lancia.myzen.co.uk/forum/index.php?topic=8106.0 I thought my wheel would need filling but by the time I pasted it with PVA and then wrapped it very very tightly and waited 24 hours, most of the gaps had disappeared, even better after a quick light sand. So didn’t need to fill it after all. I used some special clear varnish which doesn’t discolour, can’t remember if it was water based or not.