Removing the dust cover will let the telescope shed a bit of heat faster.
Many people wrap the tube is reflective insulation. This does not cool the tube faster but stabilizes the temperature inside so any tube currents are minimized.
This also helps keep the tube stable if the temperature drops/ rises quickly during a session.

 

Opening the focuser would only help slightly as the air is trapped by the primary mirror and baffle tube.
There is also the possibility of letting pollen or bugs into the tube interior so I would not recommend it.

The insulation wrap works well and lets you start viewing quicker than normal with enclosed tubes.

 

I may not be getting the idea across.
I am not a insulation salesperson but let me explain a bit more.

A SC/ Mak being an enclosed tube will typically remain above ambient temperature which causes thermal currents inside the tube. Similar to heat waves off of paving.
This can restrict the views quite considerably when wanting to do viewing at higher powers. If you set up in day time one side of the tube will be getting heated (sunlight) which will cause convection currents inside.
The insulation layer stabilizes the currents from forming inside so the observer can view at higher powers quicker.

A friend uses 140 mm and 180 mm Maks, with the insulation wrap he can be viewing just as quickly as me with my refractors.
Without the layer the telescope, depending on the internal/ external temperatures, may never reach ambient so the telescope never provides good views all night.

The only reasonably good alternative I have ever found was a device called a 'Cat Cooler' a external fan with a tube that was inserted into the telescope. It still took time to change out the internal volume of air but it was quicker than waiting for the telescope to equalize.

Now that you are probably falling asleep reading this I will stop