Wet & Dry (Sanding) Paper
Use ‘dry’ for rough sanding or for things that you don’t want to swell (e.g. wood, etc.). Otherwise try to use ‘wet’ (with water) – as this reduced friction and also creates a ‘slurry’ from the particles you have sanded…
ABS Sheet Plastic
Can perhaps find it cheaper (offcuts are sometimes on ebay). Very useful and well worth the money for a higher quality prototype.
