You can always try at your own risk
I heard a story about a 6th kyu who was being mugged and then started to do ikkyo as slowly as in dojo but it worked on the big attacker 'cause he didn't wait for that kind of move. Anyway. A sloppy technique MIGHT work BUT try training that skill that when the technique gets sloppy - you feel the arm slipping or uke resisting - back off or hit 'em. You have to be one step ahead of them from the moment you begin to counter. Only then you may be successful. And the most important thing you MUST NOT DOUBT in what you do. There is no time for doing something then doubting if it was right and then doing something else.