Lower gears are going to be harder to shift due to the greater differences in ratios. But a good GL-4 gear oil will hep make the synchros work better. GL-4 has the proper friction modifiers to let the syncro rings get enough grip to spin up their gears for smoother shifting. If it only shift harder while moving, then this might be the cause. You can also try double-clutching (or rev-matching) to help sync up the gears faster.

The real trick is to do that with the high-low range on the t-case while moving. Totally a non-synchromesh gear box, but you can shift it while moving. Have had to do that while using low range in heavy traffic, then suddenly have the traffic clear and the speeds pick up and you need to get back to high range without pulling over to stop.