Hi!
Listen Phoenix, It's as close as your workbench! Do you have a Bottle of Glue that's about three quarters used up? Good! Now take as much sprue as you can find. Put it in a large Ziploc bag. Put your hands in there(One to hold and the other to cut) and cut, The Sprue into 1/8" pieces. One very important thing to remember though.
Do NOT mix the color of sprues in the bottle. That will give you fits. One color and from one model.That is how I maintain consistancy. Now that done, You can adjust thickness also, By adding more sprue. I keep six bottles of it available. One in Clear, One in Light Grey, one in Black, One in "Daytona Red"A Revell Color that comes from the re-release of the 57/58 Cadillac Eldorado Brougham(Now by Atlantis). It's good color easily matched for continuity. Then White and lastly Moss green. It's a RailRoad color so you may want to keep another color handy.
I try to keep them Three quarters full, at all times adding a few drops of glue from time to time to freshen it. Stir well every once in a while and the stuff will last! Make sure to Cap the bottles tightly after use(Don't break the cap) but make sure it is tight. Remember, it's cheaper than the Putty, and will definitely do the job. Use the clear to build edges up where the canopy or windows don't quite match up!
The Clear is the only sensitive one. You Must use the clearest sprue at all times. Hold it to the light. If it is pure it will look a slight bit "Icy". If it isn't, it will yellow slightly in the bottle. This one also, keep in a drawer or dark spot in your work area! Drop as many pieces in the bottles to achieve the thickness you want. Seal the bags and keep the remaining for later. Don't forget to add to the bags from time to time. keep these labeled and in your work area, easy to find and then You're "Good to Go!"