Regarding the Wright engines on Connies and DC-7's. I started work in 1954 as they were being delivered to my companies customers. The 3350 was generally an easy starter due to being direct fuel injected. All the commercial models were so there was usually little technique required. The carbureted engines of both Wrights and P&W could be something else, particularly in cold weather.
On the direct injected engines it was usually not necessary to use the primer as the injection nozzles were spraying the fuel directly into the cylinder.
On carbureted engines the primer went into the blower section and the fuel had to travel a distance through the induction pipes to get to where the fire was supposed to be. Over-priming could result in raw fuel from the exhaust stacks and blower drain and a little backfire would light it off. Experience would tell you if it were necessary to use the ground fire extinguisher for if the engine caught it and ran it would blow the fire out. Fuel pooling on the ground though could make an impressive blaze. Starting a carbureted engine in very cold weather was an art and we (maintenance), sometimes had to go upstairs and assist some of our customers who normally operated in the tropical regions. The induction vibrators used to tickle the magnetos for greater output on starting would often burn out from too much use as did starters. Worst of all was opening the throttle to try to "catch" and engine on startup would caused the plugs in the cylinders to ice up. That meant a plug change or a long wait for ground heaters to warm things up.
Sticky solenoids on strarters and inverters that had stopped on a dead spot on their commutators did sometimes respond to malletizing. Plenty of same problems with the jets, pneumatic starter valves that wouldn't open.
All in all, the TC models required a lot of maintenance. The power recovery turbins (PRT) and the cooling caps cracked a lot. The blades on the PRT were extremely brittle and a little mishandling could easily damage a turbine requiring a change. Changing a Nbr. 2 released a flood of oil on top of you. Lots of cylinder cracking too. The exhaust pipes wore out at joints. We had a lot of ignition distributor changes too and there was a long period of trying different spark plugs before the right ones came along.
It was necessary to inspect the oil screens regularly and too many shiny particles or chips or even chunks signaled an internal failure and an engine change. The big Wright's were also great sludge producers, particularly the BA series and it collected in the prop domes. These had to be regularly de-sludged.
All in all, working those engines was a dirty, hard job and as a youngster I loved it.