'On a serious note, what do you recommend to prevent colours bleeding through?'
whereu - I will assume you have a dark shade & are painting with a light shade.That is not strickly 'bleeding' Then we have to ask - is it gloss? Is it enamel? Bleeding is more when a ball point or ink pen 'bleeds' through acrylic paint no matter how many coats you apply then you have to use a metho based sealer for a quick drying scenario or oil based u/coat or even a white out pen will do the trick.
If a dark shade of low sheen/matt/flat acrylic is current then 2 brush & 3 rolled coats 9 times out of 10 will cover ok or else use a tinted Dulux Total Prep (or similar product - it is white so only white base tints will be close to the desired shade) to the final coat(some u/coats suggest 'do not tint')
If you are painting a dark shade over a light shade then it depends on the base (of paint check the colour card for the type of base) you use. Some bases for bright or very bright colours mostly need a strong grey u/coat whereas bright yellow needs a white u/coat.
