My proposal is that for outdoor adventures where you are using wandering monster / random encounter tables, you should at some point plan to give these to the PCs and let them handle rolling on them, instead of spending your time doing so.
The exact trigger for this can be to your taste. It might be when the PCs pass a Natural Lore / Survival test, or when they've spent enough time tromping around in the bush, or when they find a book that details the flora and fauna of the region, or you might have a staggered revelation if you really feel the need (where the PCs receive parts of the random encounter table's total entries for each check). I recommend just handing over the list in toto though, since the whole point of this exercise is to simplify things for yourself while exciting the PCs.
This handing over represents the PCs' knowledge of the world around them - they know they're in an area threatened by goblins and wolves, with rumours of a medusa lair somewhere around, or whatever the specific monsters happen to be. Every so often, you can call for a roll on the table, which the PCs handle. You might as well get them to roll on the reaction table and the distance apart at the start of the encounter at the same time.
The trick here is that a mere roll on the wandering monster table doesn't necessarily mean the monsters themselves pop out to attack all of a sudden. I recommend you, the referee, secretly roll a d6 while the PCs are doing this. On a 1, the monster is actually there. On anything else, the PCs encounter spoor or other traces of the monsters instead. This might be a goblin campfire, a deer gnawed by wolves, or a petrified man screaming. The reaction table can either be ignored, or represent whether a reasonable observer would conclude the creature is nearby (the campfire is smoldering, vs. days old). Distance apart is how far away the PCs can see it from.
This will make your PCs paranoid and suspicious that weird and horrific stuff is about to jump out of the bush and attack them. This is the desired goal.