Brute-force missing characters from a known word?

I'm new to Hashcat and hash-cracking in general, so bear with me please.

I have a 54 character long string from which only four characters are missing; the rest are known. I also have the complete string's GOST hash. I want to know if there is a way to Brute-force the hash using the 54 character string to obtain those missing characters, and subsequently the whole string.

I tried to create a table file, but it went on to become 20+ GB huge before I quit Hashcat in fear of running out of space. I also tried to combine rules and charset by passing as a parameter and putting in the .rule file (where the missing characters are represented by * in the hash file). Apparently that's not allowed. I also don't want to go deep into shell-scripting, since that would mean learning a whole new language just to crack a code. My brain is already rattled by Python and C as it is. Oh, and I'm on Windows 8.1.

So is there a way that I've overlooked? Is there some trick or technique that you learn only from experience?

Any help is appreciated. Thanks in advance!