1. there is a few suggestions on here somehwer
2. no idea, not sure you can but maybe it is something to do with mixing, temp and humidity
3. use 'wet and dry' and water. I do it in the sink (or bath if it is my alloys). You may also want to use some soap to get a very very smooth finish. TO be honest unless you really want a glasslike dash then normal sanding is ok as plastic generally has texture and a smooth dash shows every inperfection and may look too handmade.