elrigo, first light coat on the SPONGE (Yes, you are taking off the rubber) is to soften the glue on the sponge to make it easier to roll off with your fingers or thumb. Some water based glues do not require this step, their glue build up is easy to remove. Some others are not. The rubbers assembled with rubber cement need this step to remove the glue from the sponge. Skipping this step will make you regret, because the glue on the sponge will be extra gooey and difficult to adhere the rubber back on the blade no matter how many coats you use.
Once the glue residue is removed from the sponge, a few light coats of oil are enough to expand the sponge (and the topsheet) enough to put it back on the blade and the rubber will be large enough to cover the blade. (after you allow a full day or two for the oil to absorb, then collapse any dome you made.
Tenergy is a notorious shrinker, along with some other modern rubbers. T05 requires this treatment at least once during its lifespan. Adding edge tape completely covering the sponge and a part of the side of the topsheet slows down the shrinkage some. I use 10 mm edge tape.