Ok it seems to be joining an IFR route that is the difference, what would be wrong with climbing to MSA or MORA flying the correct semi circular altitude or FL, if there is no ATC then board cast your intentions if required and continuing ? in many parts of the world there are places with no published IFR routes but you can still operate IFR outside controlled airspace especially in remote areas.
You still need to be on an IFR plan, whether or not you're in controlled airspace. You need to contact ATC to file that plan.
Also you need to be able to climb to MSA and have your clearance in VMC prior to going IMC.
Broadcasting blind is futile as for many parts of the country there is no designated frequency outside of controlled airspace.
There is a lot of IFR flight outside of controlled airspace over here. When we operate outside of controlled airspace on an IFR plan ATC will advise all known IFR traffic. The last thing you need is some clown bimbling around IMC and not on a plan as you're going past some small airfield in descent to your destination.