I'm tactical, I would wait for back up in that sort of situation then do 'cover and move' before using a flash, grenade or smoke just prior to entry. Given that maps are static, unchanging, it isn't hard to guess where the likely positions would be and to cover potential escape roots. Sadly given that players tend to be less team oriented, let alone trained in what to do, it is likely I would have to cover and move all by myself....