To make painstakingly slow progress with extremely meager or negligible results, akin to the immense difficulty of rolling a tiny mustard seed and trying to thread a needle into a minuscule opening.
这个复杂的模型构建过程，真是滚芥投针，每一步都需要极大的耐心和精准度，但效果提升却很微小。
The process of building this complex model is truly like 'rolling mustard seeds and throwing needles'; every step requires immense patience and precision, yet the improvement in effect is very minimal.
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