You can keep on using IShellItem and friends (IEnumShellItems) all along, IShellFolder is the underlying folder interface that's not easy to use, something like this (error-checks ommited):

void enumFiles(const std::wstring& folderPath)
{
    CComPtr<IShellItem> folder;
    SHCreateItemFromParsingName(folderPath.c_str(), nullptr, IID_PPV_ARGS(&folder));

    // create a bind context to define what we want to enumerate
    CComPtr<IPropertyBag> bag;
    PSCreateMemoryPropertyStore(IID_PPV_ARGS(&bag));

    CComPtr<IBindCtx> ctx;
    CreateBindCtx(0, &ctx);
    ctx->RegisterObjectParam((LPOLESTR)STR_PROPERTYBAG_PARAM, bag);
    auto flags = CComVariant(SHCONTF_FOLDERS | SHCONTF_NONFOLDERS);
    bag->Write(STR_ENUM_ITEMS_FLAGS, &flags);

    CComPtr<IEnumShellItems> items;
    folder->BindToHandler(ctx, BHID_EnumItems, IID_PPV_ARGS(&items));

    do
    {
        CComPtr<IShellItem> item;
        if (items->Next(1, &item, nullptr) != S_OK)
            break;

        CComHeapPtr<wchar_t> displayName;
        item->GetDisplayName(SIGDN_FILESYSPATH, &displayName);

        std::wcout << displayName.m_pData << std::endl;

        CComPtr<IPropertyStore> store;
        if (FAILED(item->BindToHandler(nullptr, BHID_PropertyStore, IID_PPV_ARGS(&store))))
        {
          CComPtr<IPropertyStoreFactory> factory;
          item->BindToHandler(nullptr, BHID_PropertyStore, IID_PPV_ARGS(&factory));

          factory->GetPropertyStore(GPS_BESTEFFORT, nullptr, IID_PPV_ARGS(&store));
        }

        // etc.

    } while (true);
}

int main(int argc, char* argv[])
{
    CoInitialize(NULL);
    {
        enumFiles(L"C:\\Users\\Lilo\\Documents");
    }
    CoUninitialize();
    return 0;
}

See here for more on the possible bind contexts.

PS 1: don't call CoInitalize in a library code, just call it once per process/thread.

PS 2: ATL has CComHeapPtr for smart memory pointer.