Hi yeng,
We have an article on our blog that outlines how to add a new payment gateway to PMPro: http://www.paidmembershipspro.com/2013/04/adding-a-new-payment-gateway-option-to-paid-memberships-pro/.
However, in your case, I’d say that you could use both your payment gateway of choice and the “Check” gateway. Here’s a recipe that shows how to enable more than one payment gateway for PMPro: http://www.paidmembershipspro.com/2012/06/offering-multiple-gateway-options-at-checkout/.
We also have some check level addons on Github that will help with this process of manual account activation: https://github.com/strangerstudios?tab=repositories.
Hope this helps! Let us know if you have any other questions.
Thanks
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