Hi,
I have used Adseal sealers and find them quite good.
The Rycal range has less solids than their Adseal Super Sealer which is the one I use.
I only use a roller to get a really good coat down which I think gives a better finish and with less mess.
I have also coated over previous jobs without any problems.
It is too late to use solvent sealer as others have said. I haven't used their waterbased sealer yet. They have a help line which is handy for advise when needed.