i have tried to make my own tribus before and found it very hard/not viable at the concentrations of the impello.
did you source the bacterial strains locally or from the internet?
the impello guys have a website with general guidelines for a diy innoculant based on fermented milk. theres also this guide for a myco innoculant - but dont have a guide for just powders. when i get myco on powder i just add it to the medium when i mix it. if youre doing organic you may not need the high concentration of the impello - i may be wrong but, if youre doing organics they will reproduce and sustain the population. but if youre on inorganic you need something like impello to keep population high with continuos re-applications since they cannot reproduce and die quickly in an inorganic medium.
ill be ver interested in your results, please post your progress if you go ahead with it.