Originally Posted by RBACONS

Best advice would require knowing what specific make/model radio you have and what type of retracts you have (i.e., servo driven, electric, pneumatic). For lack of any other information, if you indeed only have 1 switch and 1 knob available, it would be normal to put the retracts on the switch and the flaps on a knob. Depending on your radio, it may be possible to electronically program the knob to adjust the throws so that all the way in one direction is flaps up and all the way in the other direction is flaps down. Be aware that deploying flaps can cause a large pitch change on some models so it is usual to electronically mix in some elevator compensation with down flaps.