As for washing, I find a bendy bucket with Nikwax tech wash fine for step 1. After hand washing rinse through thoroughly. Do up the jacket, pop it on a plastic hanger. Then use TX direct Nikwax spray and give the jacket a generous squirting over the bucket, pour the run off (lots will run off!) back into the bottle and continue/use for next time. Leave to air dry, then a bit of hair dryer heat carefully applied to finish 'er off. Do this when damp, not entirely dry.
I've found this to be the most reliable way and you don't make the inside repellent like a wash in proofing.
OP a new jacket should be beading marvellous, but then again all jackets will wet through after a certain amount of downpour. It may have not had a proper DWR coating before it got to the shop. I find the rucksack area and around the zips/pockets lose their beadness first due to contact.
I use a Rab eVent jacket for walking in the mountains and a basic, slightly knackered Berghaus jacket for riding in. Repellency depends on the face being coated but not contaminated, as soon as it's dirty it can't bead! When the fabric 'wets out' it is significantly less breathable. You should therefore give the jacket a wash and reproof after every sloppy ride to maintain the performance, which seems OTT to me.
We need jackets which have a face fabric that is inherently repellent and doesn't rely on coatings. It works, but it's flawed for mucky fun.