The mú reading is the concrete-object reading - a physical mould you pour into, or by extension the 'look / cast' of someone or something. Memorise this short list and you've covered the whole reading:
模样 (look, appearance),
模子 (mould),
模板 (template, formwork),
模具 (die / mould),
倒模 (to cast). Plus the 'one-and-the-same' idioms
一模一样,
大模大样,
装模作样,
像模像样 - these all use mú because
模 here is 'mould / cast' (looking like X is cast from the same mould as X), not 'pattern / model' in the abstract sense.
