Very nice start! I like how you applied dirt to the suspension (especially the shocks)- it looks spot on accurate. And that trailer looks terrific.
Looks like you had some paint chipping here on the front door when you removed the masking-
To prevent this, after you have done the masking and before you paint, it helps to gently sand the areas to be painted with fine sandpaper (especially edges next to the tape). This gives the new paint more 'tooth' to grip, but the masking tape protects the covered areas from sanding. Also after painting and before the masking tape is removed, you can try gently running a toothpick along the edges of the tape. This helps break the edge of the paint free of the tape, before the tape gets the chance to pull the paint up with it.