Begin by extracting the data you need from Amazon Redshift. You can use the `UNLOAD` command to export data from your Redshift tables to Amazon S3. An example command is as follows:
```sql
UNLOAD ('SELECT FROM your_table')
TO 's3://your-bucket/your-prefix/'
IAM_ROLE 'your-iam-role'
PARALLEL OFF
ALLOWOVERWRITE;
```
This command exports the data as text files to a specified S3 bucket.

Once the data is in S3, you need to download it to a local or intermediate server where you have control. You can use the AWS CLI to achieve this:
```bash
aws s3 cp s3://your-bucket/your-prefix/ ./local-directory/ --recursive
```
This command copies all files from the specified S3 prefix to a local directory.

Google Pub/Sub requires data to be in JSON format. If your data is not already in JSON, you need to transform it. You can use a scripting language like Python to read the exported data and convert it into JSON:
```python
import csv
import json

with open('exported_data.csv', 'r') as csvfile:
csv_reader = csv.DictReader(csvfile)
json_data = [json.dumps(row) for row in csv_reader]

with open('data.json', 'w') as jsonfile:
jsonfile.write("\n".join(json_data))
```
This script reads a CSV file and writes each row as a JSON object to a new JSON file.

Ensure you have the Google Cloud SDK installed on your local machine or server. Authenticate your account by running:
```bash
gcloud auth login
```
Set the active project where your Pub/Sub topic resides:
```bash
gcloud config set project your-project-id
```

If not already created, set up a Pub/Sub topic in your Google Cloud project. Run the following command to create a new topic:
```bash
gcloud pubsub topics create your-topic-name
```

Use the Google Cloud SDK to publish your JSON data to the Pub/Sub topic. You can do this using a Python script with the Google Cloud Client Library:
```python
from google.cloud import pubsub_v1

publisher = pubsub_v1.PublisherClient()
topic_path = publisher.topic_path('your-project-id', 'your-topic-name')

with open('data.json', 'r') as jsonfile:
for line in jsonfile:
publisher.publish(topic_path, line.encode('utf-8'))
```
This script reads the JSON file line by line and publishes each JSON object as a message to the specified Pub/Sub topic.

Finally, verify that your data has been successfully published to Google Pub/Sub. You can list messages in a subscription to check if they are being received properly:
```bash
gcloud pubsub subscriptions create your-subscription-name --topic=your-topic-name
gcloud pubsub subscriptions pull --auto-ack your-subscription-name
```
This setup will allow you to see messages being pulled from the subscription, confirming successful data transfer.

By following these steps, you can manually move data from Amazon Redshift to Google Pub/Sub without relying on third-party connectors or integrations.