Due to the small disparities between sim and the manual for the real aircraft, that's what i usually do:
1) Set mixture to rich, prop to fine, open cowl flaps and start up. Sometimes carb heat might be needed, but remember to turn it off after starting as it can rob you of power at low altitudes. Also trim full left rudder.
2) Close cowl flaps to accelerate warm-up, step on the brakes and throttle up in steps: as soon as the gauges start bouncing around due to engine vibration (which indicates engines running rough) i stop advancing throttles and let the temps catch up, once it's warmed up a bit more and the shaking stops rinse and repeat.
3) When you reach 180-200 degrees CHT open cowl flaps, advance the throttle to obtain between 0 and +1 psi boost (about 60%) and start rolling down the runway.
4) As soon as you start picking up some speed your rudder will be effective in controlling the yawing motion caused by the props, so either adjust trim or use manual rudder inputs while advancing throttle the rest of the way.
I think we don't need that much fuel for the current map. One famous wartime raid involved an attack on the Cologne powerplants, that's the kind of distances these tanks were used for but we don't have that big a map yet.
Better to fly only on the inboard tanks and save up some weight, especially since it will translate to a shorter take-off roll and a faster transition into actual flight, where the overheating dangers are mitigated due to the increased airflow at higher speeds.
The inboard tanks are 140 gallons each (280 in total), the outboard ones are 94 gallons each (188 total). The full fuel load is thus 280+188=468 gallons.
To get the fuel percentage we need we can simply divide the gallons in the inboard tanks to the total: 280/468=0.598
So, setting fuel to about 60% should do it. I don't know if the sim will split it evenly across all tanks though but it's a small issue if it does: we might need to change over from one set of tanks to the other but other than that we'll be still flying with the correct fuel load.
I think that adding a more detailed interface for fuel in place of that slider (similar to the one we got for bombs and guns) at some point would be awesome: imagine having complete control over the contents of individual tanks, both in terms of quantity and in terms of octanes. Well, that's one for a future patch, for now just set fuel to 60% and fly
