If yours just cloudgazed, you have been lucky! Sims that come along as guests also have a tendency to walk through the portals on their own and get themselves poisoned by bees.
I always bring along at least two sims in the same household. First, for the expedition feeling. Second, while one sim hacks away at the portals, the other can pick clean the surroundings (emotion berries and dig sites.) The second sim is also useful when the first one catches fire, since in this case the shower in a can is useless.
It can also be useful to park your second or third sim at the vacation home. If you realize you need anything, the sim can order objects from the mailbox and then transfer them to the explorer's inventory. For that to work you'll have to stay in a vacation home in the same area where the jungle portal is.