Agree with ted, theres no easy way tbh. Unless you forgo it and cover it with a suitable screed that wont be affected by it. Dont quote me, but i believe you can screed over bitumen with ardex na?
Ive gone over it with na a few times for kitchen vinyls, one shop I use to work for would go over it with stopgap 300 using neat 131 when I was fitting Amtico for them. I was told you cant put any water based leveling compounds over any adhesive residues
Open the windows and use a good scraper for the worst of it and then, as you say, prime and screed. If it were a bigger job you could adopt mechanical methods like a floor grinder.
You can go over Bitumen with most screeds providing the layer is very thin. Its large build ups that cause issues. However, manufactures wont recommend this due to it would be down to the fitters 'judgement' of what is o.k. What one fitter may think is O.k may be very different to what the manufacturer says is o.k. Personally if i was going to go over bitumen i would be using Fball 200 Acrylic or Mapei Latexplan. As for removing the stuff, well this is what should happen. Very messy job as you will need to grind/shot blast it off.
200 is acrylic and allows for minor movement. But it still has a very high compression strength. (unlike most latex products) 300 doesn't like any movement.(any water based product that is apart from fibre bonded) If the bitumen gets warm (summer) it can start to move under the screed. This is a issue for the water based but the acrylic can normally cope.
Ardex claim Arditex NA is suitable: "Can be used with confidence over old adhesive residue's including bitumen and even direct on to ceramic tiles". I love this stuff, pricy though.
Be careful what your glueing to it tho, NA has a low compression strength. Fball's 200 or Mapie's Latex plan has double the compression strength and also higher flexibility shear strength.
What machine did you use mate? Did it take long and how much to hire it. Might start doing that If it's worth the price
