When you're on your own you set your own pace. Birds may not always appear to be that numerous in Brazil so you'll have plenty of time to try and work out what you're seeing.
The best way to avoid getting overwhelmed is knowing what to expect. So for the areas you'll visit, look up reports and make lists.
Once you have these lists, you'll have to start familiarising yourself. Look up what the birds look like (look at photos as well!) and in what habitat or at what height in the forest they occur (van Perlo is OK-ish, but getting the [heavy] Birds of South America (Passerines) by Ridgely and Tudor AND the [light] Birds of South America (Non-passerines) by Rodrigues Mata et al. is preferable.
Trying to learn the calls is also a good idea, but this is very difficult. Sadly, many of the tyrant flycatchers are best identified by their call (or reaction to playback!) Going to Brazil without any form of audio equipment to try and tease out an antbird or spinetail will cost you a heap of birds as well (although quite a few skulkers can be seen with time & luck).
The common birds are usually easy enough to identify. I saw the following (widespread) birds on at least 10 days during 3 weeks North-East Brazil recently:
Black Vulture, Tropical Kingbird, Lesser Yellow-headed Vulture, Turkey Vulture (these two do look very similar), Southern Caracara, House Sparrow, Sayaca Tanager, Palm Tanager, Bananaquit, Roadside Hawk, Southern Lapwing, Ruddy Ground-Dove, Smooth-billed Ani, Masked Water-Tyrant, American (Great White) Egret, Blue-black Grassquit, Pale-breasted Thrush, Great Kiskadee, Swallow-tailed Hummingbird, Grey-breasted Martin, Cattle Egret, Scaled Dove, White-browed Blackbird.
In the Southeast, Black Jacobin, Blue-and-white Swallow, Boat-billed Flycatcher, Chalk-browed Mockingbird, Red-eyed Vireo, Double-collared Seedeater, Fork-tailed Flycatcher, Golden-chevroned Tanager, Golden-crowned Warbler, Green-headed Tanager, Guira Cuckoo, Maroon-bellied Parakeet, Olivaceous Woodcreeper, Saffron Finch, Picazuro Pigeon, Plain Parakeet, Red-rumped Cacique, Ringed Kingfisher, Ruby-crowned Tanager, Rufous Hornero, Rufous-bellied Thrush, Rufous-collared Sparrow, Scaly-headed Parrot, Shiny Cowbird, Social Flycatcher, Streaked Flycatcher, Cliff (Swallow) Flycatcher, Swallow-tailed Manakin and Violet-capped Woodnymph were also common, but quite a few of these are forest birds which you will have to get into the right habitat for. It might be a start to have a look at these anyway!
Once there, write everything down, even if you don't know what you're seeing: with a reasonable description you can surprisingly often find out later what you've seen.
Starting your trip in a city with a limited amount of birds is also helpful in getting to know some of the species groups.
