Generating RSA keys and GPG keys by using external source

First of all, I am little bit short with knowledge regarding encryption, so I would need a help from you. Probably you have already seen this question somewhere, and some of you would like to say, use Google. Honestly I have looked everywhere, and there are too many confused and possibly wrong answers answering to similar questions, so I hope that someone can help me or explain it to me...

I have created TRNG file by using AM radio waves (just personal project of mine, not that I am paranoid...). ;) :D Anyway, the thing is I want to generate strongest (bit size) RSA keys using the strongest hash algorithm and to generate GPG keys but without using /dev/urandom which is pseudo random generator app, instead I want to use a file that I have created as an entropy source. Some one suggested to use

openssl genrsa -rand bits

but as I understood, this only improves /dev/urandom or /dev/random... or? Does this mean that it will "mix" random pool with this file or it will completely ignore PC pool and use the file as the main and only source? If it only mix pool with random numbers form file, is there possibility to use only file instead?

Also how can I do the same for generating GPG keys?

P.S: I know that another option would be to create my own program, reading file, putting into byte array, get random numbers from "array", etc, etc. But I use linux now and I am C# developer. (Strange combination, I know...) I would rather use faster method to generate using already created applications (if possible).

Thank you for your time, and best regards