I have been using D-76 for developing film. Recently, I have been having trouble with my images being to grainy, so I decided to try something new. I bought Acufine B/W film developer that is supposed to be ultra fine grain. I have never used anything other than D-76 and Legacy Pro for film. When my Acufine order came in, I noticed that it is to be used with a replenisher. What is replinsher, what kind should I get and how do I use it?