A friction shifter will work in that you will be able to change gears, you'll just have to be carefull you get it in the right place. Whether it will have enough cable pull to go through the full range is another matter.
I only recently learnt how to set the gears properly. I always assumed it was done at the most slack position. It's different for nearly every model. The cable tension is set in the "2" position and is relative to the position of the indicator rod compared to the axle (me not realising why it's called an indicator rod FAIL).
A friction shifter will work in that you will be able to change gears, you'll just have to be carefull you get it in the right place. Whether it will have enough cable pull to go through the full range is another matter.
I only recently learnt how to set the gears properly. I always assumed it was done at the most slack position. It's different for nearly every model. The cable tension is set in the "2" position and is relative to the position of the indicator rod compared to the axle (me not realising why it's called an indicator rod FAIL).