Drain plug tools

Most people use 3/8" - 1/2" drive ratchets or extension bars for gearbox style drain & filler plugs.
The proper plug tools can be a better fit which can save you rounding the plug out & generally make job easier on tight plugs.
Cheap sets are less than £10 & better individual socket type sets less than £25, you can even buy just the one size you need or home make one from 10.9 grade bolt with diameter slightly bigger then ground down to match the plug nice & snug & bolt hex head can be used with socket or spanner.
Freeze spray or bit of heat can be useful on stubborn plugs & in serious stubborn cases welding the homemade bolt into the plug is a solution to removal.
I use about 3 winds of PTFE tape on fitting tapered thread plugs as seals 100% with no need of over tightening plus acts as barrier between threads reducing corrosion/seized plug issues in future.

I have the set in the second picture ... had no issues with undoing any plug i got a little bar that goes through the middle but can use a 19mm socket over it for the more stubborn plugs ...

Nice to know that set quite decent.
I've come across a few stubborn plugs over the years normally due to corrosion rather than over tightening but some people go silly on them & some garages probably using air wrench on them too.

Can you elaborate on the freeze spray mate as I've never used that

Aerosol releasing freezing agent & penetrating oil.
freezing action can cause cracks helping the penetrating oil get access.
Can work quite well on small/medium nuts.
Some brands rate temps as low as -40 but your fixings don't tend to get that cold, still useful to have a can of it on the shelf though for a tricky situation.
I've used crc freeze release a few times & certainly can work/help.

I found the plugs on the gearbox really difficult. Took alot of forcing and massive extension bar to get undone when I first brought my R.

Yes I got heat on rear diff fill plug. Tip is always release the fill plug 1st as nothing worse than dropping oil only to find you can't put it back

I use these http://www.tengtools.com.au/product/6-pce-drain-plug-set-2/ Always found them to be good quality.