I just installed a Timney last week.
I got it without a bolt release.
Took the one off of my Rem Walker trigger and installed it on the Timney.
Your Timney should have a removable button head screw on the left side.
The Rem trigger bolt release is held in place by a pin and a guide stud.
The pin is held in place by a C clip on the right side.
Remove the C clip and use a small punch (or nail) to push the pin out.
Pull the bolt release away from the trigger assembly.
Push the old pin back into place displacing the punch or nail and reinstall the C clip.
Install the bolt release on your Timney.
Don't overtighten the screw or it will bind the bolt release.
The entire job takes less time than it did for me to walk out to the garage and grab the trigger and punch...