Our polling stations are either schools or church halls. Ours is a church hall.
We sometimes combine local and national elections but normally it is just the national election which obviously must cut down the time taken.
Last general election it was county elections as well but not local council elections they were held at a separate date.
Maybe you need to look at holding the elections at different times if that is possible or do the rules not allow for this.
It's never very crowded in my little town's polling place. They have paper and pen ballots that, once filled out, you feed into a machine. They always have a lot of machines. The only hold up is the old folks that check your name. They have trouble hearing in the large, noisy Nation Guard (Territorial Army) hall we vote in. I just hand them my license and point to where my name is on the list.
We have elections in other months too. Many times, these are for primary elections, or special elections for school, municipal or road bonds. These normally don't have large draws, so the few who DO vote, have the voice of the many who decide to stay at home.
One example here in Austin, Tx. was the smoking ordnance banning smoking (in any public building) a little than a year ago. That drew a small sector of the voters (less than 15 %), and the "EV Whackos" and the PETA supporters showed up in mass. I could care less what the outcome was, but a few had the say over many.
There was one restaurant that had just spent over $250,000 to install a air cleaning system for the smoking section so NO smoke would be mixed with the non smoking areas. The owners of the private business may as well had flushed the $250K down the toilets.