Hi Ellen,
Slugs feed in warmer weather. I wouldn’t bother with the beer or any other slug method. It would make no difference, even if they chewed on the leaves, since the plants are ready to go dormant and have reserved their nutrients for next year.

Is it slugs that are eating your zinnias? Japanese beetles also seem to like the plants. You can spray them with an insecticide but be careful when you do. Beneficial insects such as bees can also visit your flowers-so spray in the evening when they are done feeding. Crocosmias are a relative to gladiolus – be sure to let the foliage die back and remove only when it starts to turn yellow. They also need full sun and moist soil to grow well . Future flowering depends a lot on how the corm grew the previous year and how much nutrients were replaced. If yyour soil is poor, try feeding with a balanced (10-10-10) fertilizer to get healthier growth. Also, they should be divided every 3-4 years. Crowded corms will decline in growth and produce no flowers.

Read the article above for control of slugs.

Two soil barriers: Try crushed eggshell on the soil surface. Diatomaceus earth-a prehistoric shellfish that feels smooth but is gritty to the slug and causes them to dehydrate and die. Beer in a shallow dish buried just at soil level can attract and drown the slimy little pests. See above for more ideas.