Its not hard to get a good guesstimate of numbers even if its a bit time consuming.
In winter the ground is moist and they leave better tracks in the mud
So because boar generally hang around in sounders, except for adult males that are either completely solitary or will put up with one younger male companion ( in Portugal we call this feller the 'escudeiro' which means the knights page, they tend to push this guy into any dangerous situation as cannon fodder).
So all you need is to track different sounders, count tracks to figure out how big each one is... each one will hang out in different places usually. and then try to guess how many males should be around (this bits more difficult)...
and if thats too hard put todays technology to work, drones equipped with thermal imaging cameras will be dead easy to fly over large areas of forest to get a decent enough figure...
ffs, it really is a lack of wanting to if they cant figure this stuff out.... just go around the different paths and track after a heavy rain that will wipe out the older tracks and only leave the fresh ones...