I remember reading somewhere that all Finish soldiers KIA during this war were cared for and sent home for burial. I think the source said they were all cleaned, shaven and dressed before being sent home. Despite the cost in labor and transport such an operation would require. That source also claimed that must other nations at this time buried their common soldiers close to where they fell.
However I cant find that source again or any other sources for that matter, is it true?
Yes, this is entirely true. With the obvious exception of those whose remains could not be located or recovered, practically all Finnish war dead were repatriated and buried in their home parishes.
The policy began as an improvisation in the early days of the Winter War. There had been no official policy before the war begun, and the original idea had been to bury the dead in mass military graves close to battlefields, like the belligerents had done in the Great War. The only exception was to be made for officers, who would be transported back to their home parishes and buried with military honors. However, the rank and file detested this scheme, and since some military chaplains had already begun to repatriate the dead, and heard many a mortally wounded man wish that they could be buried close to home, full repatriation became the official policy. The dead were collected to field mortuaries which were run mostly by women Lotta Svård volunteers, washed, and dressed in white shirts, put into wooden coffins and transported via rail to the closest station.
Although some were buried in family graves, practically every Finnish churchyard old enough has a separate plot for the fallen. The dead lie buried under simple headstones that carry an engraved Cross of Liberty, the name, date of birth and date of death - no rank nor awards are shown.
Main source is this article from a Finnish magazine - but although no primary sources are given, this concurs with my earlier readings.