Yes to all, I’ve done a bunch of trips with SingleDivers.com which is large groups, a few trips with LDS’s, a local group that rents a home in Cozumel every year, Board trips (D2D) to the Channel Islands, Texas Flower Gardens, Bahamas and the Galapagos and booked a few myself with buddies I’ve met along the way.
The only trips I’ll do solo are liveaboards where it is always easy to make friends.
Booking air to some difficult spots can require an agent, Roatan Charters has actually gotten me better prices to Utila and Roatan than I could find online.
If you are putting together a trip to someplace on my wish list I will come!
If you are uncomfortable putting together all of the details Nekton Cruises and Ken at Ultimate Dive Travel have done it for trips I have been on. The one Ken put together for a D2D trip to Bali/Wakatobi was better and cheaper than the one I booked through SingleDivers. The diver just calls and says he/she is part of the group, for every ten or so there is a free spot and the group gets to divide that up to reduce our price.