I am an entrepreneur who does not like to be in the limelight. Am not a big tweeter or public figure. How can I still build my cred?
Spend zero time worrying about building your personal brand. Spend all your time focused on achieving your goals building your business. Simply put, the best way to build your brand is to achieve success. Let others evangelize you, whether it be investors impressed with your growth, customers who are delighted by the product/service you provide, or even your employees talking about what a great leader you are and what an amazing work environment you create or how brilliant you are and how you're revolutionizing the industry you're operating in.
These are all so much more important than the attention you could get by public speaking, blogging, doing interviews, etc.
A Company can be artificially inflated by someone able to create attention but it is not a sustainable path to success.
Others singing your praises is so much more substantive than promoting yourself.