In general, you cannot use NIH grant funds to pay for assistance with NIH grant proposals-because federal funds are not supposed to be used directly for obtaining additional federal funds.
BUT--those with Mentored Career Development Awards are allowed to use the award funds to pay for assistance preparing grant proposals and manuscripts for publication alike! See the page linked below:
Proposal Preparation Costs Allowable as a Direct Charge for Mentored Career Development Awards
If you're not so fortunate as to have a mentored grant, try your department chair, or even try to persuade him/her to approach instititutional officials for programmatic funds to enhance the competitive prospects of you and other faculty. Increasingly, departments and institutions are taking this approach to improving their investigators' award success rates and funding situations. Times are indeed very hard--but to those willing to invest in GrantRescue's or WinningSubmissions' services, the tiny fraction of the total funds flowing from a major grant that are represented by our fees can be highly-rewarded.