Here is one I do that I haven't read anyone else do yet.
Lay a piece of sprue about 1/2 inch from the edge of a ceramic tile, lay a piece of brass rod or tubing over on the other end. Cover this with another ceramic tile, and put it in the oven.
When it gets hot and you see one end touching the two tiles together, take it out and let it cool.
after it is cool, take the sprue off of the tiles. You now have wedge shaped seam filing plastic stock. you just apply cement to your gap, and insert the cut off pieces of wedge into the seam. Use White plastic on a Blue model, Green on a White model, etc. After each piece, you can cut and file. Now you have plastic models with the seams filled with plastic stock.
an alternate is to lay multiple pieces on the tile, pointing towards one end,,,,,,,,this gives you 1/4 inch wide pieces with a handle, just apply cement, stab the wedge into the gap, cut and save the long stub for the next baking session.
If you need a precision glue applicator and you don't have one handy for some reason, just "stretch sprue" the pipette and snip it on the narrow part,,,,,,now you have a "cementing pipette"
**this idea stolen from a ship modeler,,,,,,,,,save that flexible black sprue that some model ship parts have in them,,,,,,when you stretch that, you will have a flexible thin black line that will adhere with plastic cement
Rex