A lot of instruction on using kickers/vangs assumes you have a traveller. In that case, when close hauled you use the mainsheet to control twist by pulling the boom down, and control mainsheet angle using the traveller. The kicker is only used when further off the wind. Unfortunately this doesn't apply to our boats without a traveller - and I've never seen a very good write up of how to trim the mainsail for us.
What I tend to do is raise the mainsail pointing into the wind. Make sure the topping lift is off then winch the mainsheet to pull the boom down enough to get the desired amount of twist. Aim slightly off the wind so the sail takes shape. If you have the standard half battened sail then aim to have the top batten pointing a few degrees further out than the boom. This will probably be with the boom roughly horizontal. Now that you have the desired twist, pull the kicker through by hand to take the slack out of it, then lock it off. You have now locked-in the sail twist and can release the mainsheet to adjust the sheeting angle as desired without altering the twist. Once under way you can use more kicker to reduce twist or let some out to increase twist. It took me ages to get my head around what twist actually is since its quite hard to see the sail shape from behind the wheel. If you get someone else to helm, then go up and stand in front of the mast and look at the sail you get a much better picture of the shape and what the kicker does to change it.
For outhaul, there's a black line on the back of the boom. With the outhaul pulled back, the slider will be at the line and the foot of the sail will go straight along the boom with no belly. If you progressively let outhaul out a few inches at a time (there's a 2:1 tackle system inside the boom), you will see the foot of the sail belly out. Again, you can see this better standing at the mast. The more belly, the more power but also more drag and heel. You can buy a sticker from selden for the boom that shows how far forward of the black line you have the outhaul for reference.
In general, with very light winds, you want belly for power, but as soon as the wind gets up, you want to flatten out the sail to reduce heel so pull on the outhaul back to the black line (but not beyond or you'll stretch the sail) and flatten out the bottom half of the sail This gives you quite a lot of control before resorting to reefing, but as the wind gets up you will have to reef.
For the reefs, the outhauls work the same way to control belly, but since its windy enough for a reef you probably want a flat sail so yes, get it on reasonably tight - but you must let the kicker off a bit and go through the process of setting twist again after the reef us in.
Generally speaking, in very light winds you want sails that are full of shape for max power so lots of belly. As the wind picks up you want flat sails for less power and less heel, then smaller flat sails via reefing.
It took me years to get comfortable with understanding the impact of kicker and outhaul on the bav30, and it also takes a couple of trips at the start of each season to re-remember! I found the yellow rya book "sail trim for cruisers" quite good. But definitely stick tell tales all over your sails and look at the mainsail from the mast to see how complex the shape of it us.
Same goes for headsail and mucking about with genoa car position - you get a great view from inside the front cabin looking up out of the hatch.
Since Windermere is long and narrow with high hills either side, is it the case that the wind us either on the nose or directly behind, and you are either close hauled or running?
