Donegal is a brilliant destination, worth it just for the walk on the beach. Yes,the runway really is a bit hard to spot from the NE, especially with low sun, but you can't go wrong if you tune in the Localizer or use GPS. Do be aware of the mountains not far to the East of the Airport, which can produce some 'interesting' turbulence if the wind is from the South or East.
I suggest routing direct across Northern Ireland. Aldergrove Approach provide a good ATSOCAS as far as Eglinton. Do note the new Eglinton CTA - Class C within the Shannon FIR - and note the VMC criteria that apply therein up to FL75. Eglinton will clear you through and usually hand you off to Shannon Low Level, but as you are in Class G at that point I often just pick up the Donegal ATIS and then call them up directly.
Finally, remember to use the semi-circular rule for VFR in the Shannon FIR.