After an initial early period when the equipment was hard to come by and crews were assembled haphazardly, the artillery of the RCW was able to do anything that a WWI battery could. That doesn't mean that they used all the techniques very much in practice.
Indirect fire could be pre-planned. But that was only really helpful if the situations of a prepared defence – which was very much the exception rather than the rule. Prepared assaults were even less common.
The issue was whether there had been time to lay down the required telephone nets, position FOOs and establish a plan. RCW front lines did not generally stay still for very long, so that was rarely the case.
Artillery was overwhelmingly used in direct fire mode, or at least just behind a crest with an observer only slightly in front. There simply wasn't time to do otherwise in most battles. Open field counter-battery fire was therefore quite common.
Batteries had FOOs, but using them required time to set up a line so even when used they often weren't far away.
The Top War article is good, but after correctly saying that the artillery was largely used in small packets (rarely larger than battery) it then spends excessive time on all the exceptions.
The one army that tended to use WWI doctrine was the Poles. The result was that they generally were unable to get decent artillery support. By the time the artillerymen had got themselves settled the battle had moved on. The Reds, in contrast, got much more value from their artillery, despite having less of it, because their guns followed their forces and fired immediately from positions at or near the front lines.
The very big gun armoured trains were a bit different. They did use FOOs with telephones because they could carry all the equipment and their guns' long ranges meant they could continue to fire even if the lines moved a bit.
