An after-shave lotion generally is an alcohol-based solution because that alcohol speeds up evaporation, which in turn more rapidly cools the skin. Cooling the skin helps to reduce blade rash caused by having too close a shave.
Check the alcohol content of Dettol and also see whether it is viscous (thick liquid). Looks to me like a soap, which if true means it has some high molecular weight components, usually long-chain aliphatic acids or esters. A viscous fluid is not so good as an after-shave because slow flow usually goes hand-in-hand with slower evaporation. Now if the thick liquid contains some type of skin conditioner, MAYBE it would be OK.