Thank you for the advice,
i understand your opinion to apply wet mud on the vehicles.
But in my opinion there is a chance to lose detail if you apply a bit mud.It's a personal preference i think.
Now, how do i make the pine trees ????
Step 1 , i use Balsa wood as the basis of the trunk. Then sanded with fine sandpaper.

Step 2 , i'll make a mixture of filling compound + thinner (to make it smooth) and fine sand. than apply this on the trunk , this makes the tree bark more realistic.
After drying the trunk is sprayed over in a red brown color and furder modified with som pigment.

Step 3 ,
with a fine needle or thumb nail making holes in the trunk
The twigs are from a toy store for model trains and are a kind of sea vegetation.
After they have been ranked from largest to smallest , i glued them in the trunk with instant glue.
I hope this was useful ?
Greets