I was having a hard time figuring out how to upload an image to Twitter with a progress callback. Turns out I wasn't far off, just needed to convert my SLRequest to an NSURLRequest and then AFNetworking(godbless you) does the rest with progress blocks.

sendTwitter.m

-(void)sendTwitter {
    ACAccountStore *account = [[ACAccountStore alloc] init];
    ACAccountType *accountType = [account accountTypeWithAccountTypeIdentifier:
                                  ACAccountTypeIdentifierTwitter];
    
    [account requestAccessToAccountsWithType:accountType options:nil completion:^(BOOL granted, NSError *error) {
        if (granted == YES) {
            NSArray *arrayOfAccounts = [account accountsWithAccountType:accountType];
            if ([arrayOfAccounts count] > 0) {
                twitterAccount = [arrayOfAccounts lastObject];
                
                NSString *status = @"Secrets";
                UIImageView *uploadImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 640, 480)];
                UIImage *uploadImage = [image resizedImageToFitInSize:uploadImageView.bounds.size scaleIfSmaller:NO];
                
                NSURL *requestURL = [NSURL URLWithString:@"https://upload.twitter.com/1.1/statuses/update_with_media.json"];
                
                SLRequest *postRequest = [SLRequest
                                          requestForServiceType:SLServiceTypeTwitter
                                          requestMethod:SLRequestMethodPOST
                                          URL:requestURL parameters:nil];
                [postRequest addMultipartData:UIImageJPEGRepresentation(uploadImage, 0.6) withName:@"media[]" type:@"multipart/form-data" filename:nil];
                [postRequest addMultipartData:[status dataUsingEncoding:NSUTF8StringEncoding] withName:@"status" type:@"multipart/form-data" filename:nil];
                [postRequest setAccount:twitterAccount];
                
                NSURLRequest *preparedRequest = [postRequest preparedURLRequest];
                
                AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:preparedRequest];
                
                [operation setUploadProgressBlock:^(NSUInteger bytesWritten, long long totalBytesWritten, long long totalBytesExpectedToWrite) {
                    NSLog(@"Sent %lld of %lld bytes", totalBytesWritten, totalBytesExpectedToWrite);
                }];
                [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
                        NSLog(@"Twitter upload success");
                        [self completedSendingPhotos];
                    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
                        NSLog(@"Twitter upload error");
                    }];
                 
                [operation start];
            }
        }
    }];
}