Best Cockroach Killer Gel/ Paste. Apply Roachgo gel amply behind and under the following: stove, refrigerators, sinks, washing machine, water pipe, sewers, manholes, electrical conduit, corners of cabinet, closets, Remove drawers from cabinets, apply freely into corners of drawer walls. Reapply every 40 to 50 Days. Remove excess gel and dispose into garbage. Best Cockroach Killer Gel at low Cost.