To get the use of the file a currentrecid inside an inline you do the follwoing.
[fmp-inlineaction: -db=mydatabase.fp5, token.1="{currentrecid}", fieldtosearch="valuetofind", -find]
If you want to pull information from file a into your found results to show different info you use the { } tags. ie you have a field in file a that you want to use as an if statement(on my site a candidate says he is interested in consulting. I find his record and then on my page I do a search of the company database and of the info found I want to show the consulting departments phone number as that is what the guy is interested in) ou have to use tokens and the { } tags in the inline. Therefore unfortunately limiting yourselve to 10 fields you can use.
[fmp-inlineaction: -db=companydatabase.fp5, industry="{fmp-field: industry}", -token.1=(fmp-field: industry}", -find][fmp-record][fmp-if: currrenttoken:1.eq.consulting][fmp-field: consulting_phone_number][/fmp-if][/fmp-record][/fmp-inlineaction]
Hope that helps