This one can be surprisingly effective.
Ask yourself a simple question and give yourself about five seconds to start answering.
Not five seconds to construct the perfect sentence.
Five seconds to start talking.
For example:
Что ты любишь?
shto ty LYÚ-bish?
What do you like?
Five…
Four…
Three…
Я люблю кофе.
ya lyu-BLYÚ KÓ-fye
I like coffee.
Good enough.
The point is to train yourself to respond rather than endlessly build the perfect sentence in your head.