You can easily alodine 2 RVs with a quart of alodine using my procedure of dipping a 2" brush into a cup of alodine and applying on maybe a 2' x 2' block and then continuing to rebrush the same area keeping it properly wetted during the recommended dwell time. Then rinse and dry off, then continue on to the next block. This procedure optimizes a uniform, goldfish tinge on the aluminum which promotes a tanecious bond to the epoxy primer if primed within the four hour window, are else re- alodine.
Even brushing/scrubbing the alodine won't bite thoroughly without first using the phosferic acid wash ( the blue stuff) to clean the aluminum.This is after scotch padding and wiping down with a gun cleaning solvent. If I remember correctly, the acid wash is diluted with four parts water, alodine used full strength.
So, what I'm recomendind is: scotch padding, wipe with solvent, acid wash, alodine, prime within 4 hours. BTW, I always sand the primer. It's work but yields a nicer paint job and helps minimize orange peel. Oh, I forgot, before scotch padding, wipe down using a oil/wax/contaminant cleaner or else you're just working the contaminants into the metal making it difficult to properly clean for a good alodine.
One may ask if a proper alodine is worth all this. I say absolutely. I once saw a nice RV8 at a Flyin that was painted with a gunn steel metallic paint that had actually partly blow off and had to be repainted. The paint was beautiful, it just had no bond.
I'm currently rebuilding a 6 that was damaged where the process I'm describing was used. Even where the skins were creased abruptly (destroyed) the paint did not let go or peel back, just cracked open.
For us builders who want to paint your on aircraft and are maybe jack legs like myself, we first must understand that accomplishing a good bond on aluminum is a different ball game. All the efforts will show 5 years down the road after your aircraft has endured some wear and tear. Don't skimp on the prep!!!