Gradually reduce speed until freeze frame

Hold down the R key and select a range in the clip. Then go to the toolbar and click on the speed button that looks like a watch face. Speed adjustments will apply only to the range you selected. Repeat as needed.

I took a clip and made a range selection of a third of the clip in the middle of the clip. I set that at 80%. Then I left the front third at normal. Then selected the last third and set it at 60%. The clip played smoothly through the speed changes.

You can make only one range selection at a time in a single clip. You can do three steps by selecting the range for the second step. Then click on the watch face in the tool bar and select custom. Make a percentage change which will retime the range selection of the clip but you will see on the clip a speed adjustment button at the top of the clip for each section of the clip so you can set as desired.