Starting large radials
In the dim past I flew a 4 engine a/c which had Wright R3350 engines, which are similar to those on the P47. The R3350 had oil seals in the supercharger which did not seal properly until there was significant oil pressure. Consequently, there was always a large puff of smoke on start.
It's also true that large radials, due to the less controlled cylinder/head temperatures (compared to liquid cooled engines) had larger tolerances between moving parts, and this led to more oil getting past the valves and cylinder rings. For the R3350, acceptable oil consumption in flight was 3 gallons per hour, although we would not normally see more than 1. Our aircraft had 80 gallon oil tanks per engine.
As for being hard to start, I don't have any recollection of that, at least in summer temperatures. Arctic conditions are a different story, and starts were always sporty there, even when we had taken precautions. There is a reality show running called "Ice Pilots NWT" which features a Yellowknife based airline operating WWII transports. The frequent starting issues shown on that show seem realistic.
Merlins, BTW, were no easier to start in the Arctic. They do at least have the advantage of a wonderful sound when running.