Never force any shift lever. If it doesn't go in, it's because things are not aligned properly.
In this case, the 4WD lever, if it's hard to get it and out, then there is a lot of tension on that drive line to disengage or the teeth are lot aligned properly to engage. The loader trick works great. Another one is to just go forward a little bit, then stop, go backwards slowly while applying gentle pressure on the lever to either engage or disengage.
The more you get to know the tractor and it's quirks, the easier it gets.