SGC,
Cellulose is a single-part product based on cellulose (surprise, surprise) derived from vegetable matter. I'm sure with your aviation knowledge you know that.
In aviation circles it is used in dopes and in automotive circles it was used in car paints (but the latter have switched to water-based acrylics).
To others, particularly Peter337:
If the paint is a true 2-pack (i.e. with a paint and a catalyst [hardener]) then once it is cured it can be overcoated with anything if it is is keyed (sanded or de-nibbed) properly.
Etch prime is not 2-pack (it doesn't catalyse), it is 2-part (i.e. 2 parts that do not chemically combine), so beware using it if you need a solid substrate to a top coat.
Further 1, if your zinc chromate primer comes in spray cans, it is for the large part completely useless, since the decent properties it used to hold were banned by treaty years ago. Get a spray gun and use 2-part etch prime.
Further 2: Etch prime is hygroscopic. It absorbs moisture, so do not use it on steel or aluminium without overcoating it. It must be covered within 16 hours with a primer (or top coat). If in excess of 16 hours, then it must be keyed with 600 grit (or de-nibbed with Scotchbrite), or alternatively a quick flash coat of fresh etch prime before immediately coating with your chosen primer.
I always overcoat etch prime with a 2-pack epoxy glazing primer, but 2-pack acrylic primer would do.
If you intend using a 2-pack finish coat (gloss coat), then a single-pack acrylic primer will do, as it means you don't have to sand it down) then apply your modern automotive gloss coat colour-matched to your existing paint scheme.
Sorry if this is long-winded.
Russ