To be on the safe side put a 60W bulb in the water/utility bay to keep your pump and lines functioning. Pulling in slides does help. Depending on how many slides you have, maybe try pulling in 1/2 of them or do all...it's your choice and once the cold arrives, you'll know what helps and what doesn't. The largest slides let in the most cold.
Keep all glass well covered. But, be prepared for frozen condensation on all glass and window frames. Let them thaw and dry them off during the day then close up again.
If the cold last quite a while...consider taking showers at a bath house to reduce indoor humidity. But a propane furnace will dry out the air. To know for sure...have an indoor humidistat.
Also drain and unhook your sewer hose.
Leave at least one cabinet door under all sinks open.
Do not leave a faucet dripping.