What I have to say is probably not IMBA standard, but it works well when I have used this technique.
As a general rule when building you never want to place logs on the lower edge of a trail as they collect a build up of silt and sediment creating mud for tyres to sink into.
I have been building constantly for about 3 years or so now and have found that when a trail is extremley rocky a solid log on the lower edge of a trail is actualy one of the best things to do, probably the only time you would consider it.
You will probably end up finding a tree on the lower edge of your trail to rest your log against.
Once you have your log in place just build up/armour your trail with some of the flatter and larger rocks in the area you are working on.
you will need to bed these in firmly.
Then fill in any remaining gaps with smaller rocks untill you have a smoothish even surface and cover over with dirt, clay, just no plant matter or black soil if you can help it... although sometimes you will need to just use whatever you are working with.
Compact it down firmly. (A
firerake works well for this)
If built right and with water flow in mind you should end up with an armoured section of trail that hopefully catches sediment, but will have rock below to stop tyres sinking in. (A genuine best of both worlds scenario)
also if you are working in extremley rocky areas sometimes a full wheel barrow is not the easiest thing to navigate through rough trail areas.
I made myself a
stretcher for shifting rocks/dirt. a person at each end moves alot of soil in a very small ammount of time, just choose a strong fabric.
I ended up using shade sail/sunscreen material and two lengths of aluminium tubing for mine.
I hope this can help you out.