One thing I've been noticing lately is that all fur shaves differently. Which is why people get so stuck.
To shave thinner density furs like bigzs short shag line. You absolutely must use a 7FC blade rather than the 10 blade the Andis clippers come with.
Step 1. Trace your pattern onto a small square of fur. Don't cut out the pattern yet
Step 2. With a 7fc blade shave with the fur as normal
Step 3. Brush the fur the opposite direction and then shave across the fur in all direction barely hovering over top.
This takes practice. Give it a few tries!