Recipe: Grandma's Fruitcake Recipe didn't tell how to make starter

I am SO glad I stumbled on this link! I read the post from Betty in Finchville, Ky and the reply from Linda Lou in WA regarding the Friendship Fruit Compote/Starter. I am excited because I'm hoping my search for a starter has been solved here. Please let me know if this will work or if anyone has any other ideas. As you'll see just to try without first asking everyone's advice would be quite a lengthy risk.
I never liked fruitcake until I tried my husband's grandmother's. I only tasted it to be polite and really enjoyed it. She called it friendship cake and gave me a jar of pink liquid (the starter) and the following recipe. Later I asked her how she made the starter but sadly her memory was failing her by then and she hadn't written it down. Since her passing I inherited her recipes but even with this recipe in her own hand she has nowhere included HOW to make the starter.
An elderly woman I care for claims to have a recipe for starter but can't remember where she put it- just that it included a "cake of yeast".
I remember Grandma keeping a very large jar(old pickle jar)on her kitchen counter with the fruit fermenting for her cake. I wrote down Betty's recipe and Linda Lou's reply. Do you think that'll work for this cake? Is Grandma's recipe ok to leave on the counter in a closed jar as she did? It really is worth the investigating- not just sentimentally to me but it is delicious.
Thank you for reading my long post and for any input. You're welcome to Grandma's recipe- I hope we'll all get to enjoy it.

GRANDMA'S FRIENDSHIP CAKE (As she wrote it)

**Use WOODEN spoon to stir

To make brandied fruit:
1 1/2 cups starter juice
3 1/2 cups sugar
1 large can peaches with juice*

*(or about qt. home canned -
8 halves or 2c chopped with 1 c. juice)

Cut peaches into small cubes.
Stir daily for 10 days.


On 10th day:
Add 3 1/2 - 4 cups sugar
and 1 lg. can Pineapple chunks or fruit cocktail, drained
Stir daily for 10 more days.

On the 20th day:
Add 2- 9oz. jars of maraschino cherries, chopped, no juice.
Stir daily for 10 more days.

On the 30th day:
Drain fruit and save juice for starter to give to a friend.

To make cake:
1 1/2 cups brandied fruit
1 box yellow cake mix (Duncan Hines)
1 box butter pecan instant pudding**
4 eggs
2/3 c vegetable oil (Wesson)
1 c chopped pecans
**(or 1 box vanilla or butterscotch pudding with 1 more Tablespoon chopped pecans if you can't find butter pecan instant pudding)

Mix together and pour into greased tube or bundt pan. Bake at 325 degrees for 45-60 minutes. After you make your cake you will have enough fruit for 2 more cakes.