A couple of examples I tried. This idea I did see on youtube so I can't take credit I'm afraid.Now that's an idea I will try.
I use milk bottle tops for the same reasons. We get through so much milk in our household that I've seriously considered investing in our own cow, so I'm never short of tops.I save Water bottle caps to put a little paint in and also I use them to put glue in
......... I also like using Baking Soda and Super Glue mixture for filler.
Thinking that I might have to try these ones for casting, as the Revell Plasto is just too soft to work with (having a 50% shatter rate) and it's so annoying to have filed to the point of 'almost there' to have the bit fall apart (top one is now in 3 bits!)i use talcum powder when i need a super hard filler
I keep my beer bottle caps for that purpose, and it gives me an excuse - "I need to drink a beer this evening I need another bottle cap for paint mixing"I save Water bottle caps to put a little paint in and also I use them to put glue in and use with a Cocktail stick to apply.