you can down shift into 1st if you hold the clutch until you decelerate to a certain RPM, but expect inevitable jerk... I would not recommend it for slowing down at all, unless you can anticipate the reaction.

I rev match most of the time, but double clutch occationally.

 

I always double clutch going down, from 6-2.Brakes before going into 1st.

 

I downshift into first only in heavy traffic to keep the car moving at a slow, slow speed instead of coming to a full stop.