Spread Biscuit Slot Glue
4. Apply Glue With An Acid Brush
Glue must be evenly applied throughout the biscuit slot to get
the strongest joint possible. The easiest way? Squirt some glue into
the slot and then run a glue brush, sometimes called an acid brush,
through the slot until the glue is evenly coated on both sides and the
Source: Highland Hardware, (800) 241-6748
Glue brushes, #166025, $3 for 10; #107792, $10 for 50.