We motored to Haines from Des Moines last summer (June 7 - July 22) in our R25.
The advice on using Slowboat is solid. There are several itineraries on their website and key advice on the various "gates" (Strait of Georgia, Dent/Yuculta Rapids, Queen Charlotte Strait and Dixon Entrance).
We had the benefit of Neap tides which made the transit through the rapids a "piece of cake".
Other resources that are recommended include the current edition of Ports and Passes, Waggoner Cruising guide, Exploring Southeast Alaska, North Coast and South Coast of BC (three book set by Douglas) and the Navionics app on your smartphone/tablet.
Cell coverage is spotty and be certain to verify that your data coverage includes Canada. We used the Garmin InReach with the subscription to access weather when cell coverage was lost. This was occasionally frustrating as the Garmin wouldn't consistently report the marine forecast.
Getting weather and seas information was frustrating. We learned to collect as much information as possible when we were within cell coverage. Unfortunately this sometimes resulted in using long term forecasts that were not longer valid for the actual conditions.
A good tool box and spare parts are strongly recommended. For our 2013 diesel this included fuel filters, oil filter, belts and impeller in addition to the fluids. We had a alternator tensioner pulley failure that kept us in Ketchikan longer than planned. Alaska Airlines Gold Streak membership (recommended) saved the day by allowing us to expedite shipping of the replacement part.
In closing I would add that we had the advantage of traveling during the year of Covid which meant that there were no issues getting moorage. We may have been the first and last vessel to travel through BC without restrictions (until we reached the north side of the Queen Charlotte Strait where the Indian ports were closed to all travelers, including the RCMP). Only Shearwater and Prince Rupert were open. Be sure to hit the hot springs in this part of BC.
Safe travels and don't forget to get your sport fishing licenses for Canada and Alaska.