If it is of any help; you can use clear masking fluid over DI products. Coat each area separately. Clear Masking Fluid Is Permanent but if you wanted to you can stamp over with Archival Ink.
I also use Tim Holtz Distress micro Glaze with success.
As to tissue paper - anything goes - it really does. My preference is the tissue that they wrap you wine bottles in (if you can find an Off Licence nowadays). Otherwise the tissue wrapping paper they sell in WHS
I still only use Satin Glaze (PaperArtsy) or Liquitex fluid medium. I think the clue is in the word fluid. I find Mod Podge or any other PVA type medium to be too heavy for the tissue leaving it more likely to tear and can give a lumpy finish