First take guidance from any forum linked to RTI..post the facts, get proper guidance on maintainability of such case. Then go for writ, only after exhausting the process laid down in RTI.
The remedy under RTI is only as stipulated in that Act. One can file writ after SIC/CIC decision and not before that.
If you wanted to file PIL, then the documentary evidence may help you in filing the PIL and then it is not RTI.
There is no separate advdocate only for RTI/PIL. You can also approach High Court Legal Services Authority and find out a qualified litigant for filing PIL in his name.