I have a wafer thin Mulberry document bag. Bought it many years ago, before they became fashionable. Believe the early stuff was all made in the UK. Anyway, a lot of their leather has a slightly pitted surface, into which RM Williams saddle dressing spreads evenly, but does tent to dry with whitish spots. Best solution has been for me to condition just once a year, during the hottest months. I leave the bag in direct sunlight by the window to warm up first. Same with the tin of dressing. Just use your common sense, old rags and lots of buffing. A day outside in really hot weather fully sets and cures it. Simple. Just be aware that my Mulberry has darkened/ patinated quite considerably since new. Must be down to the suns rays on the leather + RMW dressing, as the same conditioned area under the main flap is much lighter in colour.
No real reason as to why I use RMW dressing. Always have and probably always will. The only thing I don't use it on is RMW boots... go figure.
This probably isn't as much off-topic as might appear... same rules apply to conditioning your shoes, whatever your choice of product.
I bought a big container of RMW Leather Conditioner from the Manhattan RMW store 3-4 yrs ago. I really like it. I use Obenauf on work boots and other leather items that need weatherproofing but not on calfskin leather shoes and boots. For those items, the RMW conditioner seemed to work well, smell good and certainly hasn't "hurt" any of my calfskin footwear. That said, Saphir has taken the place of RMW's conditioner in many cases but the RMW product still has a place in my kit.
Like many of us, I've come to the conclusion that [generally speaking] the brand of product is less important than the methods employed (i.e., use conditioners/products in moderation, remove salt, dirt, etc. after each use, brush regularly and use conditioners/products in moderation). There are exceptions of course, but most quality products will do the job if the user knows what he is doing.