Here’s a sentence from a recent translation with a good example of a synecdoche and how I chose to deal with it. The context is a football tournament involving schools from different countries:
All the games were played in good spirit, with Spain’s San Juan

[school] handing out school crests to all their opponents and St Joseph’s [school] giving each school a specially made trophy to commemorate the event.
I’ve highlighted the synecdoche in this sentence in bold: a whole (a school) is used for a part (the schoolchildren). As an aside, a synecdoche can also use a part for a whole (the Crown = the monarchy). I was unhappy with keeping the synecdoche in my translation, as I thought the result was clumsy. The possessive form Spain’s San Juan was difficult to translate without using the word école, which led to an awkward des fanions à ses couleurs and to unpalatable repetitions:
Tous les matches se sont déroulés dans un bon esprit : l’école espagnole de San Juan a distribué des fanions à ses couleurs à tous ses adversaires et St Joseph’s a offert à toutes les écoles un trophée spécialement conçu pour commémorer cet événement.
Normally, when I’m faced with repetitions, such as in this example, I try and use synonyms. However, it was difficult to find a synonym for école; établissement was a contender, but with spécialement and événement in the same sentence, the assonance wasn’t pleasant at all. The sentence was also too long. However, when you’re stuck, I find that writing a first (tentative and unsatisfying) translation is a good way to move on and try and work out a solution to difficult structures.
I chose to forget about the synecdoche and to give back the schoolchildren the role which was rightfully theirs during the event. The advantage was that the sentence flowed better and that I could easily find what I would call "contextual synonyms" (words that can be used as synonyms but only in a particular context) for the schoolchildren (joueurs, adversaires, homologues, élèves). The long sentence was hard to split, so I replaced et by tandis que, which allowed me to add a comma and a bit of breathing space. This was the result:
Tous les matches se sont déroulés dans un bon esprit : les joueurs espagnols de San Juan ont distribué des fanions aux couleurs de leur école à tous leurs adversaires, tandis que les élèves de St Joseph’s ont offert à leurs homologues un trophée spécialement conçu pour commémorer cet événement.