Both 糊 (こ) and 塗 (と) are standard on'yomi. 糊 means paste, and 塗 means to smear or paint. Wrong readings like ことく mispronounce 塗, and こぬり uses a kun'yomi. It means to gloss over, cover up, or temporarily conceal a mistake or defect without genuinely solving it, implying a superficial fix.

糊 (こ) も 塗 (と) も標準的な音読み。糊を塗って一時的に隠すイメージ。失敗や欠点を一時的にごまかすことです。