The best advice I can give you, and I'm talking out of pure experience built up from hundreds of hours, don't use EF6.
Forget about EF6 when dealing with something that just needs a little bit of logic applied to it.
Use either the good old approach ADO.NET or a MicroORM that can do the mapping for you. I can assure you that the time spent writing either ADO.NET or throwing a bit of investigation after a MicroORM are well spent and you will reach your milestones much quicker and without any blackbox magic :)