First clean the plate, but if you use a mobile phase mix take care, that the final clean up run is made with dry methanol.
Draw a fine pencil line using the softest graphite pencil and no mechanical forces. Take a micro brush no. 1 and the sample solutions. Six lines of sample solutions, 10 mm each plus 5 mm distance from line to line are “written” onto the layer along the graphite line. If one line should have a double sample concentration draw above the dry first one the same sample a second time. By this way you can even “write” a calibration line.
“Write” with a micro brush no. 6 or higher a methanol “line” near to the sample lines. Do not move over parts of the sample position. The brush edge must remain about half to one mm apart from the sample lines. The methanol phase line will broaden quickly. The speed with which you “write” the line is about 2 mm / sec but a few training minutes will give you the necessary feeling. You will have optimized this type of an easy procedure (compared to Chinese hand writing) soon after some tests.
The lower part of all sample line pieces are already focussed. Now the plate should already be made dry with a hair dryer BUT NOT with hot air. Clever hair dryers have temperature levels adjustment and correct is room temperature. This one works in a few minutes. If the line pieces are still wet from methanol, focussing will not succeed into a very sharp sample line as seen in Figure 5 below.
This is just the same procedure as used in figure 2 but now methanol is focussing the sample lines from the lower position. If everything works as it should, you have all six sample lines compressed to sharp lines and pushed correctly into the chromatography start position. Now the plate must again be blown totally dry using room temperature air from the cold hair dryer. Than the plate should look like shown in figure 5. If the focussed sample lines are NOT accurately positioned, a final focus run is possible in a TLC tank with methanol.
What have we achieved ? The same result could be expected by using a sample line spraying system as commercially available ?
Probably not. Spraying may cause electric fields which may result in substance specific losses at sampling. Even a soft air movement causes specific sample losses. The sprayed line is definitively very much thicker than the double focussed line reducing drastically the separation efficiency especially in the lower Rf range. And what about the economy ?